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\begin{document}


\def\RunningAuthor{Mohini Anandrao Salunke et al.}
\firstPage{2507}
\articleType{Review Article}
\receivedDate{30 Sep 2021}
\acceptedDate{02 Nov 2021}
\revisedDate{01 Nov 2021}
\journalVolume{2021, 12}
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\journalDoi{ijrps.v12i4.4896}
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\title{\textbf{Neoteric Approaches for Extraction of Bioactives from Marine Macroflora}}
\author{Mohini~Anandrao~Salunke\textsuperscript{*}\textsuperscript{1},  
            Balaji~Sopanrao~Wakure\textsuperscript{2}, 
            Pravin~Shridhar~Wakte\textsuperscript{1}~\\[5pt]{\textsuperscript{1}University Department of Chemical Technology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad- 431 004, Maharashtra, India}~\\{\textsuperscript{2}Vilasrao Deshmukh Foundation, Group of Institutions, VDF School of Pharmacy, Latur- 413 531, Maharashtra, India}}

\begin{abstract}
More than 70\% of the earth's surface is covered by the marine ecosystem. This habitat is home to a large number of marine species that produce very different metabolites as defense mechanisms. In recent years, a lot of research work has been done on the extraction of biologically active compounds using various methods in many commercial areas such as biomedicine, pharmaceuticals, cosmetics, nutrition and health care and chemical industry. In fact, many traditional extraction methods have several limitations, such as low efficiency, high energy costs, and low yields. Therefore, there is an urgent need for new and updated extraction methods. Because conventional extraction methods are solvent-intensive and time-consuming, consequently this review covers neoteric approaches like pressurized liquid extraction (PLE), ultrasonic assisted extraction (UAE), enzyme assisted extraction (EAE), extraction with supercritical fluids (SFE) and microwave assisted extraction (MAE) and working mechanism to extract bioactive components from marine flora. The advantages of the new technology include higher output, less time and lower cost. In addition, different combinations of new extraction technologies and technologies suitable for heat-labile compounds have also been identified. This article summarizes the most important bioactive compounds in marine flora and the latest developments in new extraction techniques.
\end{abstract}\def\keywordstitle{Keywords}

\begin{keywords}Marine Macroflora,\newline Neoteric Extraction Methodologies,\newline Ultrasound-Assisted Extraction (UAE),\newline Supercritical Fluid Extraction (SFE),\newline Microwave-Assisted Extraction (MAE)
\end{keywords}
\twocolumn[ \maketitle {\printKwdAbsBox}]
\makeatletter{\raggedright\textsuperscript{*}Corresponding Author\par Name:\ Mohini~Anandrao~Salunke~\\ Phone:\ 9168680404~\\  Email:\ mohinisalunke82@gmail.com
        \par}\vspace*{-11pt}\hrulefill\par{\fontsize{12}{14}\selectfont ISSN: 0975-7538}\par% 
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\section{Introduction}
Marine flora includes microflora (bacteria, actinomycetes, cyanobacteria and fungi), microalgae and macroflora as macroalgae (seaweed), flowering plants (mangroves and other halophytes). The ocean occupies nearly 70\% of the world's land and has rich biodiversity, of which only microflora and microalgae account for more than 90\% of the marine biomass. This vast array of marine plant assets will provide enough opportunity for the revelation of new drug. It is being widely recognised that the ocean includes a significant number of natural products and new chemical entities with distinct biological activities, which could aid in the discovery of possible medications with greater efficacy and specificity for treating human ailments.

The existence of a 3.5-billion-year-old marine flora on Earth is clear, and it is still nature's best supply of chemicals. To withstand the drastic fluctuations in pressure, salinity, and temperature that are typical in their habitat, marine species generate new chemicals, for example polyphenols, polysaccharides, carotenoids, and omega-3 fats, and the resulting molecules are complex and distinct in structure as well as functional qualities \unskip~\citep{1263261:23637046}.

Marine flora represents a large number of biologically active chemicals that can be employed for anti-aging, anti-oxidation, anti-microbial, anti-proliferation, anti-inflammatory, anti-diabetic and neuroprotective activities. People are increasingly interested in new products that contain various biologically active compounds with potential biological activity \unskip~\citep{1263261:23637045}.

For example, the use of biologically active compounds in a variety of commercial fields like biomedicine, pharmaceuticals, cosmeceuticals, nutrition and healthcare, and the chemical industry necessitated the development of sophisticated and cost-effective methods to extract these biologically active ingredients. In this regard, a combination of appropriate, selective, cost-effective, and environmentally friendly extraction processes is required \unskip~\citep{1263261:23637044}.

Traditional extraction processes, such as Soxhlet extraction, solid-liquid extraction (SLE), and liquid-liquid extraction (LLE), use huge volumes of solvents and take a long time to complete. The extraction efficiency and selectivity of biologically active compounds are often low using these methods.

Furthermore, because traditional extraction processes are rarely automated, their reproducibility may be compromised. Modern technologies (supercritical fluid extraction (SFE), subcritical water extraction (SWE), Ultrasonic Assisted Extraction (UAE), and Microwave Assisted Extraction (MAE) should be utilised to extract these chemicals \unskip~\citep{1263261:23637043}.

Extraction processes that were appropriately devised and implemented are critical to end product's quality. Various influencing parameters, such as the physical and chemical qualities of source materials, matrix properties, solvent type and concentration, pH, temperature, pressure, and time, all have an impact on the extraction process' overall performance.

The total extraction effectiveness is primarily decided by following factors: (a) key input parameters; (b) knowing the source's nature; (c) the process-source interaction; (d) chemical action of the biologically active molecule \unskip~\citep{1263261:23637044}. To obtain extracts containing desired biologically active compounds, each method's process parameters must be modified.

In comparison to previous reviews, this one is unique in the following ways: (a) To extract seaweed, a systematic introduction of selected process parameters of SFE (temperature, time, pressure, use of co-solvent), SWE (temperature, time, pressure, solids-solvent ratio), UAE (temperature, time, frequency, power, solid-solvent ratio), and MAE (temperature, time, frequency, power, solvent type) should be used; (b) reporting main categories or individual compounds extracted with their biological activity (if demonstrated); (c) updating available reference. Among other things, it can be a good solution to the complications that regular extraction processes cause \unskip~\citep{1263261:23637042}.

\textbf{Extraction Methods}

The first step in extracting the desired natural substance from the raw material is extraction. Solvent extraction, distillation processes, pressurization, and sublimation based on extraction principles are examples of extraction procedures. Solvent extraction is the most prevalent approach.

The extraction of natural products entails the following steps: (a) the solvent penetrates the solid matrix; (b) the solute is dissolved in the solvent; (c) the extracted solute diffuses out of the solid matrix; and (d) the extracted solute is collected. Any elements that promote diffusibility and solubility in the preceding phases will make extraction easier. The nature of the extraction solvent, the particle size of the raw material, the solvent to solid ratio, the extraction temperature, and the extraction time all influence extraction efficiency \unskip~\citep{1263261:23637041}.

When it comes to solvent extraction, it's critical to pick the right solvent. When selecting a solvent, selectivity, solubility, cost, and safety should all be taken into account. According to the rule of likeness and mutual solubility, solvents with polarity values similar to the polarity of the solute may perform better, and vice versa (like dissolves like). Alcohols (EtOH and MeOH) are universal solvents utilised in phytochemical studies for solvent extraction.

The extraction impact is generally better when the particle size is smaller. Since the permeability of the solvent and the diffusibility of the solute are improved, the small particle size will increase the extraction efficiency. However, a particle size that is too fine will cost too much solute absorption in the solid, and it is difficult to perform subsequent filtration.

Solubility and diffusion will increase as the temperature rises. On other hand, too high temperatures, can cause solvent loss, resulting in the extraction of undesired impurities and the degradation of heat-labile components.

With increasing extraction duration within a given time range, extraction efficiency improves. Increasing the duration after the solute balance is achieved inside and outside the solid material has no effect on the extraction. The higher the solvent to solids ratio, the better the extraction yield; however, an excessively high ratio will result in excessive extraction solvents and a long concentration time.

The current extraction methods can be divided into two categories: traditional/conventional methods and alternative/unconventional methods. Traditional methods include maceration, decoction, infusion, pressing, percolation, Soxhlet extraction, water distillation, etc. Non-conventional extraction methods include EAE, MAE, UAE, SFE and PLE technologies.

Traditional procedures for extracting biologically active components from marine plants include maceration, decoction, infusion, Soxhlet extraction, and hydro distillation.

\textbf{Maceration}

Maceration is an ancient simple technique used in the preparation of medicines \unskip~\citep{1263261:23637040}. The sample is macerated with solvent and then filtered or centrifuged. Returning the tissue residue to the extraction container, it is extracted once more. This process is repeated until there is no longer any extraction yield. 

To enhance solvent penetration, the sample is frequently chopped into small pieces or crushed into fine particles. To speed up the diffusion process, stir or sonicate the mixture \unskip~\citep{1263261:23637039}. \ensuremath{^{}}

The solvent of choice in most circumstances is methanol or ethanol. However, a sequence of solvents of increasing polarity are frequently utilised to produce a specific degree of fractional distillation. To speed up the filtration process, filter aids and vacuum are frequently used. 

To avoid compound degradation, the solvent is evaporated by rotational evaporation at a temperature of not more than 35\ensuremath{^\circ}C after extraction. This procedure is fairly straightforward and does not necessitate the use of any specialised equipment.

Shaking occasionally throughout the maceration process can help with extraction by improving diffusion and eliminating concentrated solution from the sample surface, bringing more solvent into the menstruum and resulting in a higher extraction yield. It has the potential to extract thermolabile chemicals \unskip~\citep{1263261:23637038}.

\textbf{Percolation}

Percolation is more successful than maceration because it is a continuous process in which saturated solvent is continuously supplied by new solvent \unskip~\citep{1263261:23637041}.

\textbf{Decoction}

This is an effective approach for extracting water-soluble components that are not damaged by heat. During the decoction, distilled water is added to the dried extract, and the combination is boiled at 100\ensuremath{^\circ}C for an extended period of time. The filtrate was then allowed to cool to ambient temperature before being filtered. To make an extract, the filtrate was concentrated \unskip~\citep{1263261:23637037}.

\textbf{Infusion}

The solid particle is submerged in lukewarm or hot water for a small duration in this process of extraction \unskip~\citep{1263261:23637037}.

\textbf{Reflux Extraction}

Percolation or maceration are less effective than reflux extraction, and it takes short period and uses less solvents. It can't be utilised to extract natural compounds that are heat-labile \unskip~\citep{1263261:23637041}.

\textbf{Soxhlet Extraction}

The Soxhlet extraction uses principles of reflux and syphon to constantly extract the flora with new solvent, combining the benefits of both reflux and percolation. Soxhlet extraction is a high-efficiency continuous extraction technology that is automated. When compared to maceration or percolation, it takes less time and uses less solvent. Thermal deterioration is more likely in Soxhlet extraction because to the high temperature and long extraction period \unskip~\citep{1263261:23637041}.

The Soxhlet extraction method is the first method to extract lipids proposed by the German chemist Franz Ritter von Soxhlet \unskip~\citep{1263261:23637038}. It is being utilised to extract bioactive (solid-liquid) chemicals from a variety of natural resources. Soxhlet extraction is easy to use. The extraction procedure can be done indefinitely with fresh solvent until all of the solute in the raw material has been used up \unskip~\citep{1263261:23637036}.

\textbf{Hydro Distillation and Steam Distillation}

These are common techniques for extracting volatile oil. Some natural compounds will decompose in HD and SD. Hydro distillation is a traditional method of extracting metabolites from marine flora that does not use organic solvents \unskip~\citep{1263261:23637037}. In hydro distillation, the marine floral material is placed in a steel chamber, and sufficient water is added, and then boiled or inject directly steam into the floral sample.

The release of biologically active chemicals in floral tissues is mostly influenced by steam and boiling water. The vapor mixture of water and oil condenses when water is cooled indirectly. The condensing solution goes from the condenser to the separator, which automatically separates the oil and biologically active chemicals from the water \unskip~\citep{1263261:23637035}. The advantages and disadvantages of various conventional methods of extraction were presented in Table1.


\begin{table*}[!htbp]
\caption{\boldmath {Advantages and disadvantages of the conventional methods of extraction} }
\label{tw-1fe7350243b0}
\def\arraystretch{1.1}
\ignorespaces 
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\begin{tabulary}{\linewidth}{p{\dimexpr.23030000000000005\linewidth-2\tabcolsep}p{\dimexpr.3670000000000001\linewidth-2\tabcolsep}p{\dimexpr.40269999999999996\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Extraction Technique & Advantages & Disadvantages\\
\tblmidrule 
Maceration &
  Simple method &
  $\bullet$~The extraction time is long, sometimes several weeks.~\newline $\bullet$~Low extraction efficiency.\\
Decoction &
  $\bullet$~It does not necessitate additional and costly equipment.  ~\newline $\bullet$~It is simple to execute. &
  It is not recommended to extract thermolabile or volatile components.\\
Soxhlet extraction &
  $\bullet$~The sample communicates quickly with a fraction of fresh solvent, assisting in the transfer of equilibrium to the transfer solvent.~\newline $\bullet$~There is no need to filter the data after extraction with this method.~\newline $\bullet$~The matrix veggie has no effect on the Soxhlet. &
  $\bullet$~The duration is long, and the amount of solvent extracted is large, leading to economic losses and environmental issues.~\newline $\bullet$~The samples are heated at a high temperature for an extended period of time. As a result, if the plant material contains heat-stable chemicals, the risk of thermal damage to particular compounds cannot be overlooked.~\newline $\bullet$~The latter evaporation/concentration is limited due to the huge volume of solvent used.\\
Hydro distillation and steam distillation &
  Commonly used methods for the extraction of volatile oil. &
  Extraction at a high temperature can result in the loss of some volatile components. Because of this flaw, it can't be used to extract heat-sensitive chemicals.\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}
Solvents, high temperatures, and/or stirring are used in all of these processes. Furthermore, traditional approaches are typically manual processes, making reproducibility difficult. The heating method destroys the biological activity of sensitive biologically active substances (such as fucoxanthin), resulting in a low extraction rate. The pH, temperature, and pressure conditions utilised can alter the active molecules. In addition, the required organic solvents are harmful to the environment. The United States Environmental Protection Agency, for example, has classified n-hexane as the most harmful of 189 hazardous air pollutants (HAP). As a result of these constraints, as well as the significant increase in demand for\textbf{\space }biologically active substances from marine flora, it is necessary to develop appropriate, selective, cost-effective, and environmentally friendly extraction technologies that are fast, produce higher yields, and comply with applicable laws and regulations.

\textbf{Neoteric Methods of Extraction}

There are also so-called green extraction technologies, which are concerned with the development and discovery of energy-saving extraction technologies. Extraction may be made safe and high-quality by combining alternative solvents with renewable natural resources. Many novel extraction techniques exist, and they are likely to meet many of the parameters listed above. EAE, MAE, UAE, SFE, and PLE technologies are among them. These technologies will be explored in terms of their principle and mechanism of action, as well as their benefits and drawbacks compared to older approaches and the possibility for extracting biologically active chemicals from marine flora.

\textbf{Pressurized liquid extraction (PLE)}

PLE was first reported for use in extraction of biologically active substances in 1996 \unskip~\citep{1263261:23637034}. The most promising approach for obtaining biological active substances from various source materials is extraction \unskip~\citep{1263261:23636994}. 50-200\ensuremath{^\circ}C and 3.5-20 MPa are the temperature and pressure settings employed in PLE, respectively. Pressure is applied to the liquid in PLE to allow it to be utilised at temperatures higher than its typical boiling point. When compared to typical extraction techniques, which take 10-48 hours and use up to 300 ml of solvent, the combination of high pressure and high temperature allows for a faster extraction process with less solvent (for example, utilising 10-50 ml of solvent in PLE for 20 minutes).


\begin{table*}[!htbp]
\caption{\boldmath {Pressurized liquid extraction of bioactive Compounds from marine flora} }
\label{tw-f076eb56ab8a}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.1807\linewidth-2\tabcolsep}p{\dimexpr.12659999999999998\linewidth-2\tabcolsep}p{\dimexpr.20659999999999997\linewidth-2\tabcolsep}p{\dimexpr.07690000000000001\linewidth-2\tabcolsep}p{\dimexpr.06619999999999998\linewidth-2\tabcolsep}p{\dimexpr.07230000000000004\linewidth-2\tabcolsep}p{\dimexpr.1512\linewidth-2\tabcolsep}p{\dimexpr.11950000000000001\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Species & Compounds & Solvent & \textit{P} & \textit{T} & Time & Flow Rate & \cAlignHack Ref\\
\rowcolor{kwdboxcolor} &  &  & (bar) & (\ensuremath{^\circ}C) & (min) & (g/min) & \\
\tblmidrule 
\textit{Phaeodactylum tricornutum} \mbox{}\protect\newline Bohlin  &
  Fucoxan- thin &
  EtOH &
  103.4 &
  100 &
  30 &
  Static &
  \cAlignHack \unskip~\citep{1263261:23637033}\ensuremath{^{}}\\
\textit{Undaria pinnatifida} &
  Fucoxan- thin\textit{ pinnatifida} &
  DME with or without 10\% \mbox{}\protect\newline EtOH \mbox{}\protect\newline DME + EtOH 10\% \textsection  &
  40 &
  60 &
   &
   &
  \cAlignHack \unskip~\citep{1263261:23637032}\ensuremath{^{}}\\
\textit{Phormidium sp}. &
  Fatty acids &
  \textit{ n}-Hexane, \mbox{}\protect\newline \textit{ n}-hexane: EtOH (1:1), \mbox{}\protect\newline limonene, \mbox{}\protect\newline limonene: EtOH (1:1) \mbox{}\protect\newline Limonene: EtOH (1:1) \textsection  &
  207 &
  50-200 \mbox{}\protect\newline 200 \textsection  &
  15 &
  Static &
  \cAlignHack \unskip~\citep{1263261:23637031}\ensuremath{^{}}\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Supercritical fluid extraction of bioactive Compounds from marine flora} }
\label{tw-687be4a43d4a}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.1503\linewidth-2\tabcolsep}p{\dimexpr.1526\linewidth-2\tabcolsep}p{\dimexpr.14590000000000002\linewidth-2\tabcolsep}p{\dimexpr.0919\linewidth-2\tabcolsep}p{\dimexpr.0941\linewidth-2\tabcolsep}p{\dimexpr.12559999999999999\linewidth-2\tabcolsep}p{\dimexpr.1066\linewidth-2\tabcolsep}p{\dimexpr.133\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Species & Compounds & Cosolvent & \textit{P} \mbox{}\protect\newline (bar) & \textit{T }(\text{\textordmasculine}C) & Time (min) & CO2 Flow Rate \mbox{}\protect\newline (g/min) & \cAlignHack Ref\\
\tblmidrule 
\textit{Paracoccus} \mbox{}\protect\newline \textit{zeaxanthini- faciens} &
  Zeaxanthin &
  Acetone, water, \mbox{}\protect\newline EtOH, MeOH, \mbox{}\protect\newline isopropyl alcohol \mbox{}\protect\newline MeOH \textsection  &
  100-500 \mbox{}\protect\newline 300 \textsection  &
  40-80 \mbox{}\protect\newline 40 \textsection  &
  40-160 + 20 \# \mbox{}\protect\newline 160 + 20 \textsection  &
  0.36-1.79 \mbox{}\protect\newline 0.90 \textsection  &
  \cAlignHack \unskip~\citep{1263261:23637030}\ensuremath{^{}}\\
\textit{Nannochlorop- sis gaditana} \mbox{}\protect\newline L. M. Lubi\'{a}n &
  Carotenoids and chlorophyll a &
  EtOH 5\% \mbox{}\protect\newline 15 &
  200-500 \mbox{}\protect\newline 500 \textsection  &
  40-60 \mbox{}\protect\newline 60 \textsection  &
  15+180 \# &
  0.20 &
  \cAlignHack \unskip~\citep{1263261:23637029}\ensuremath{^{}}\\
\textit{Callinectes sapidus} \mbox{}\protect\newline Rathbun &
  Astaxanthin &
  EtOH 10\% &
  295-345 \mbox{}\protect\newline 340 \textsection  &
  45-65 \mbox{}\protect\newline 45 \textsection  &
   &
  3.4-4.8 f &
  \cAlignHack \unskip~\citep{1263261:23637028}\\
\textit{Chaetoceros muelleri} \mbox{}\protect\newline Lemmermann &
  Fatty acids &
  EtOH &
  200-400 \mbox{}\protect\newline 400 \textsection  &
  40-80 \mbox{}\protect\newline 40 \textsection  &
  15+45 \# &
   &
  \cAlignHack \unskip~\citep{1263261:23636993}\ensuremath{^{}}\\
Hypnea charoides &
  Fatty acids &
   &
  24.1-37.9 &
  40-50 &
  120 &
   &
  \cAlignHack \unskip~\citep{1263261:23636992}\\
\textit{Cladophora glomerata, Ulva flexuosa,} \mbox{}\protect\newline \textit{Chara fragilis} &
  Carotenoids, phenols &
  EtOH [0{\textendash}15] &
  10-30 &
  40-60 &
  120 &
   &
  \cAlignHack \unskip~\citep{1263261:23637027}\\
\textit{Sargassum muticum, Sargassum vulgare,} \mbox{}\protect\newline \textit{Hypnea spinella, Porphyra sp.,} \mbox{}\protect\newline \textit{Undaria pinnatifida, Chondrus crispus,} \mbox{}\protect\newline \textit{Halopytis incurvus } &
  Isoflavones &
   &
  10-40 &
  35-75 &
  10-60 &
   &
  \cAlignHack \unskip~\citep{1263261:23637026}\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Ultrasound-assisted extraction of bioactive Compounds from marine flora} }
\label{tw-2f50acc3d987}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.14\linewidth-2\tabcolsep}p{\dimexpr.1682\linewidth-2\tabcolsep}p{\dimexpr.13489999999999998\linewidth-2\tabcolsep}p{\dimexpr.1682\linewidth-2\tabcolsep}p{\dimexpr.1298\linewidth-2\tabcolsep}p{\dimexpr.11690000000000001\linewidth-2\tabcolsep}p{\dimexpr.142\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Species & Compounds & Solvent & Ultrasound \mbox{}\protect\newline Power (W) & \textit{T} \mbox{}\protect\newline (\ensuremath{^\circ}C) & Time \mbox{}\protect\newline (min) & \cAlignHack Ref\\
\tblmidrule 
\textit{Cylindrotheca Closterium }(Ehrenberg) Reimann \&\textit{\space } J. C. Lewin &
  Fucoxanthin and chlorophyll \textit{a} &
  Acetone &
  4.3-12.2 \mbox{}\protect\newline 12.2\textsection  &
  8.5 &
  3-15 \mbox{}\protect\newline 5 \textsection  &
  \cAlignHack \unskip~\citep{1263261:23637025}\ensuremath{^{}}\\
\textit{Dunaliella salina }(Dunal) \mbox{}\protect\newline Teodoresco &
  Carotenoids and chlorophylls &
  MeOH, \mbox{}\protect\newline DMF b \mbox{}\protect\newline DMF \textsection  &
   &
   &
  3 &
  \cAlignHack \unskip~\citep{1263261:23637029}\ensuremath{^{}}\\
\textit{Phaeodacty- lum tricornutum }Bohlin &
  Fucoxanthin &
  EtOH &
   &
  23 &
  30 &
  \cAlignHack \unskip~\citep{1263261:23637033}\ensuremath{^{}}\\
\textit{Laminaria japonica} \mbox{}\protect\newline Areschoug &
  Carotenoids and chlorophyll \textit{a} &
  MeOH &
   &
   &
  30 &
  \cAlignHack \unskip~\citep{1263261:23637012}\ensuremath{^{}}\\
\textit{Dunaliella tertiolecta} \mbox{}\protect\newline Butcher &
  Fatty acids &
  Chloroform/ MeOH (2:1) &
  320-400 \mbox{}\protect\newline 370 \textsection  &
   &
  4-6 \mbox{}\protect\newline 5 \textsection  &
  \cAlignHack \unskip~\citep{1263261:23637023}\\
\textit{Tetraselmis suecica} \mbox{}\protect\newline Kylin (Butch) &
  Fatty acids &
  Water &
  500-1000 \mbox{}\protect\newline 1000 \textsection  &
   &
   &
  \cAlignHack \unskip~\citep{1263261:23637022}\ensuremath{^{}}\\
Ascophyllum nodosum, \mbox{}\protect\newline Laminaria hyperborean  &
  Polyphenols, laminarin &
  200 (distilled water \mbox{}\protect\newline and 0.03 M HCl) &
  Ultrasound probe; \mbox{}\protect\newline 20; \mbox{}\protect\newline 750 &
   &
  15 &
  \cAlignHack \unskip~\citep{1263261:23637021}\ensuremath{^{}}\\
Gelidium pusillum &
  Phycobili-proteins &
  100 (phosphate \mbox{}\protect\newline buffer 0.1M) &
  Ultrasonic bath; \mbox{}\protect\newline -41.97 &
  30, 35 and 40 &
  2, 4, 6, 8 and 10 &
  \cAlignHack \unskip~\citep{1263261:23637020}\ensuremath{^{}}\\
Sargassum muticum, \mbox{}\protect\newline Osmundea pinnatifida, \mbox{}\protect\newline Codium tomentosum &
  Total phenolics, \mbox{}\protect\newline antioxidants, prebiotic \mbox{}\protect\newline compounds &
  50 \mbox{}\protect\newline (Deionized water) &
  Ultrasonic bath; \mbox{}\protect\newline 50/60; \mbox{}\protect\newline 400 &
  50 &
  60 &
  \cAlignHack \unskip~\citep{1263261:23637019}\ensuremath{^{}}\\
Laurencia obtuse &
  Phenolic compounds, \mbox{}\protect\newline antioxidants &
  10-30 (95\% ethanol) &
  Ultrasonic bath; \mbox{}\protect\newline 40; \mbox{}\protect\newline 250 &
  30-50 &
  30-60 &
  \cAlignHack \unskip~\citep{1263261:23637018}\ensuremath{^{}}\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Microwave-assisted extraction of bioactive compounds from marine flora} }
\label{tw-5b638569470b}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.1657\linewidth-2\tabcolsep}p{\dimexpr.1361\linewidth-2\tabcolsep}p{\dimexpr.1182\linewidth-2\tabcolsep}p{\dimexpr.1798\linewidth-2\tabcolsep}p{\dimexpr.13739999999999998\linewidth-2\tabcolsep}p{\dimexpr.14389999999999999\linewidth-2\tabcolsep}p{\dimexpr.1189\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Species & Bioactive Compounds & Solvent & Microwave Power (W)/  \mbox{}\protect\newline Frequency [MHz] & \textit{T} \mbox{}\protect\newline (\ensuremath{^\circ}C) & Time \mbox{}\protect\newline (min) & \cAlignHack Ref\\
\tblmidrule 
Ulva meridionalis, Ulva ohnoi, Monostroma \mbox{}\protect\newline Latissimum  &
  Poly-saccharides (ulvan and rhamnan sulfate) &
  Water &
  1000; \mbox{}\protect\newline 2450 &
  100-180 &
  10 &
  \cAlignHack \unskip~\citep{1263261:23637017}\ensuremath{^{}}\\
Sargassum thunbergii &
  Poly-saccharides &
  Water &
  200-800; &
  10-90 &
  10-50 &
  \cAlignHack \unskip~\citep{1263261:23637016}\ensuremath{^{}}\\
Enteromorpha prolifera &
  Polyphenols &
  10-60\% ethanol &
  300-700 &
   &
  5-40  \mbox{}\protect\newline (1-4 cycles) &
  \cAlignHack \unskip~\citep{1263261:23636991}\ensuremath{^{}}\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Enzyme-assisted extraction of bioactive compounds from marine flora} }
\label{tw-3f29a48317db}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.25\linewidth-2\tabcolsep}p{\dimexpr.25\linewidth-2\tabcolsep}p{\dimexpr.33519999999999996\linewidth-2\tabcolsep}p{\dimexpr.1648\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Marine Algae & Bioactive \mbox{}\protect\newline Compound & Enzymes Used for Extraction & \cAlignHack Ref\\
\tblmidrule 
Undaria pinnatifida &
  Fucoxanthin &
  Alginase lyase enzymes, temperature of 37 \ensuremath{^\circ}C, and pH of 6.2 &
  \cAlignHack \unskip~\citep{1263261:23637015}\ensuremath{^{}}\\
Brown seaweed species &
  Antioxidant \mbox{}\protect\newline rich extracts &
  Carbohydrases and proteases &
  \cAlignHack \unskip~\citep{1263261:23636990}\ensuremath{^{}}\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}
High temperatures diminish the solvent's viscosity and surface tension, facilitating the process for solvent to reach the matrix region and therefore boosting the extraction rate. PLE, however is usually recognised as a green extraction technology, owing to its low usage of organic solvents and compliance with all basic pollution regulations \unskip~\citep{1263261:23637013}.

Although lengthier extraction durations are sometimes required, the overall extraction time is usually 15-45 minutes. The PLE procedure, like SFE, can be run in both dynamic and static modes. To achieve the best recovery rate, various parameters can be tuned. The extraction solvent, temperature, pressure, static time, and cycle count are the most critical factors to consider. Other factors, such as purge duration and flushing volume, have little impact on the final recovery rate and are usually left alone \unskip~\citep{1263261:23637034}.

PLE is more adaptable than SFE when it comes to the extraction solvents that can be, allowing it to extract a wider range of physiologically active chemicals. The solvent in PLE will be chosen based on the polarity of the target chemical. This method, on the other hand, is significantly less efficient than SFE. 

The bioactive compounds extracted from marine flora using Pressurized liquid extraction techniques were enlisted in Table~\ref{tw-f076eb56ab8a}.

\textbf{Supercritical Fluid Extraction (SFE)}

SFE makes use of supercritical fluids, which have both liquid-like and gas-like features above their critical point, like as solvent strength and low surface tension, along with better transport performance \unskip~\citep{1263261:23637012}.

A thick non-condensable fluid is defined as a supercritical fluid (SF). When temperature and pressure of a fluid surpass the applicable critical temperature and pressure, it is said to be supercritical. Only a single phase exists at the critical point, with some characteristics of liquids (density) and others of gases (viscosity, compressibility, and mass diffusion coefficient) \unskip~\citep{1263261:23637011}. Furthermore, in comparison to other extraction method, SFE uses the least amount of solvent and can be used to extract a wide spectrum of biologically active chemicals \unskip~\citep{1263261:23637010}.

Because of its favourable Tc and Pc (31.1\ensuremath{^\circ}C and 73.9 bar), CO2 is the most often employed supercritical fluid for extracting thermally unstable chemicals. Furthermore, supercritical CO2 has a low viscosity, a low surface tension, a high diffusivity, and a low density. It's also non-toxic, non-flammable, inexpensive, simple to acquire, and chemically inert under a variety of situations. It retains its gaseous state at normal pressure and temperature, obviating the need for solvent evaporation following extraction \unskip~\citep{1263261:23637009,1263261:23637008}.

In addition, carbon dioxide provides a non-oxidizing atmosphere in the extract, thereby preventing the degradation of the extract \unskip~\citep{1263261:23637007}. The biggest limitation of supercritical CO\ensuremath{_{2}} is that it is not suitable for extracting polar compounds \unskip~\citep{1263261:23637008}. 

The density of the fluid can be adjusted by changing the temperature and pressure of the fluid, which is a key aspect of SFE. 

This means that variations in temperature and pressure can affect the fluid's solvency, which is determined by the fluid's density \unskip~\citep{1263261:23637006,1263261:23637005}.

The bioactive compounds extracted from marine flora using Supercritical Fluid Extraction techniques were tabulated in Table~\ref{tw-687be4a43d4a}.

\textbf{Ultrasound-Assisted Extraction (UAE)}

Ultrasound assisted extraction (UAE), also known as ultrasonic extraction or ultrasonic processing, uses ultrasonic energy in the extraction process. Ultrasound accelerates the dissolution and diffusion of solutes and heat transfer in the solvent, thereby improving the extraction efficiency. Another advantage of the UAE includes low solvent and energy consumption, as well as reduced extraction temperature and time.

The UAE is suitable for the extraction of thermally unstable compounds. UAE is commonly used to extract many types of natural products \unskip~\citep{1263261:23637004}. The acoustic cavitation in the solvent caused by ultrasonic waves is primarily responsible for the improved extraction obtained with ultrasonic waves. Ultrasound also has mechanical effects (it breaks the cell wall), which allows the solvent to infiltrate the tissue more deeply, increasing the surface area of contact between the solid and liquid phases. It will help the solute diffuse quickly from the solid phase to the solvent \unskip~\citep{1263261:23637003}.

The particle size of the plant extract, the moisture concentration, and the solvent used all influence the extraction process in the UAE.

Different bioactive compounds extracted from marine flora by Ultrasound assisted Extraction techniques were presented in Table~\ref{tw-2f50acc3d987}.

\textbf{Microwave Assisted Extraction (MAE) }

Microwaves are non-ionizing electromagnetic radiation with frequencies from 300 MHz to 300 GHz. The method of extracting various compounds using microwave was first reported in 1986 \unskip~\citep{1263261:23637002}. In MAE, both heat and mass gradients work in the same direction, but in conventional heating, they work in opposite directions \unskip~\citep{1263261:23637001}. As a result, only the surface of the substrate is directly heated in traditional heating, and subsequent heating is accomplished through conduction from the surface of the substrate particle to the core. MAE, on the other hand, generates direct heat in the matrix by causing friction between polar molecules\unskip~\citep{1263261:23637000}.

Microwaves are included in two oscillating vertical fields, namely (1) electric field and (2) magnetic field, according to general physics and microwave theory. The former is thought to be the source of the heating problem \unskip~\citep{1263261:23636999}. Furthermore, two mechanisms govern the heating principle: (1) dipole rotation and (2) ion conduction \unskip~\citep{1263261:23636998}. 

To conclude, marine sources are great candidates for MAE extraction of physiologically active chemicals due to their high moisture content. This is because the primary target of microwave heating is moisture. Water evaporates and creates a lot of pressure after microwave heating, which finally ruptures the outer cell membrane and allows biologically active substances to leak out \unskip~\citep{1263261:23636997}. 

The bioactive compounds extracted from marine flora by microwave-assisted Extraction techniques were presented in Table~\ref{tw-5b638569470b}.

\textbf{Enzyme Assisted Extraction (EAE)}

The structure of cell membranes and cell walls, micelles formed by macromolecules such as polysaccharides and proteins, and protein coagulation and denaturation at high temperatures during the extraction process are the key challenges in extracting natural products. EAE can improve extraction efficiency by hydrolyzing cell wall components, cell membrane, and intracellular macromolecules, hence facilitating the release of natural compounds \unskip~\citep{1263261:23636997}. Cell wall degrading enzymes (such as carbohydrases and proteases) have been found to decompose cell walls and release required biologically active substances in marine flora under optimal temperature and pH conditions, it may be utilised to impregnate tissues and decompose the cell walls of natural substrates.

The cell walls and stratum corneum of seaweeds are made up of chemically complex and heterogeneous biological components, therefore this is especially significant. In other words, proteins and different binding ions are linked to sulphated and branched polysaccharides (including calcium and potassium). To extract biologically active chemicals from marine algae, it is important to decompose these complex compounds. Viscozyme, Cellucast, Termamyl, Ultraflo, carragenanase, agarase, xylanase, Kojizyme, Neutrase, Alcalase, and Umamizyme are some of the most often used enzymes \unskip~\citep{1263261:23636996}. 

Several parameters must be considered in this regard in order for the extraction process to be effective: Temperature of the reaction, time of extraction, pH of the system, enzyme concentration, and particle size of the substrate \unskip~\citep{1263261:23636995}.

Various bioactive compounds extracted from marine flora by Enzyme assisted extraction techniques were presented in Table~\ref{tw-3f29a48317db}.
    
\section{Conclusion}
Contrast to traditional methods, modern extraction methods do not require organic solvents. Therefore, these methods have proven to be less time-consuming and eco-friendly techniques for extracting biologically active substances from marine macroflora. The high yield obtained using modern methods significantly improves the extraction efficiency. Modern extraction methods (such as UAE, MAE, SFE, and PLE) have been characterised as green extraction methods in recent years. They've gotten a lot of interest in current history because of increased extraction rate, selectivity, target extract stability, and process safety benefits. PLE and SFE methods are extremely sensitive methods, in addition to saving time and lowering solvent use. They can be altered by changing the solvent's pressure and temperature (in PLE and SFE), adding co-solvent (in SFE), or changing the solvent altogether (for PLE). CO\ensuremath{_{2}} is the most commonly employed supercritical fluid in CO\ensuremath{_{2}}-SFE because it is non-flammable, non-toxic, and affordable, as well as having a low and easily accessible critical temperature (31.2\ensuremath{^{0}}C) and critical pressure (7.4 MPa) that may generate non-toxic, solvent-free extract. Pressurized liquid extraction with dimethyl ether (gas at normal temperature and pressure) will not produce the toxic effects of harmful solvents. The high temperature operation of MAE and PLE is the main obstacle to its application to heat-labile compounds. For industrial applications, EAE has advantages such as reduced extraction time, reduced solvent usage and increased yield. The UAE has been used industrially to extract biologically active compounds from natural resources. The field of extraction of biologically active compounds develops with the development of smart solvents. These amazing, powerful and highly selective solvents can be tailored to the matrix being studied, and nowadays, a large number of solvent combinations can be used to selectively extract specific classes of compounds. By using mechanical (MAE and UAE), electrical (PEP) and enzymatic (EAE) methods, higher extraction rates can be obtained while reducing the extraction time. In short, regardless of the source, in the near future, biologically active ingredients, so-called "biologically active compounds", will become the norm rather than a niche. In addition, the growing scientific and practical understanding of green extraction technology has provided deep insights and attention to the field of marine-derived biologically active chemicals. Further investigations in this sector should focus on overcoming the problems of using these new technologies on a large scale so that the industry can take dominance of the huge benefits derived from the extraction of bioactive substances from algae. 
    
\section{Acknowledgement}
The authors are thankful to Vilasrao Deshmukh Foundation, Group of Institutions, Latur, Maharashtra, India and University Department of Chemical Technology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, Maharashtra, India for technical support.

\textbf{Conflicts of Interest }

The author(s) declare that there is no conflict of interest. The authors alone are responsible for the content and writing of this article.

\textbf{Funding Support }

The authors declare that they have no funding support for this study.
    

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