## 3 Proanthocyanidins  
Proanthocyanidins (also known as condensed tannins) are pigmented polymerised polyphenic compounds that contribute to the antioxidant action and cardiovascular disease-preventing properties of botanical extracts, and these medicinal properties make them interesting for the pharmaceutical industry [26; 27; 28]. [PERSON] et al. [7] reviewed the reported health benefits linked to proanthocyanidins, and found that besides antioxidant and cardiovascular protective functions, condensed tannins have cancer-preventing, neuroprotective, and antimicrobial properties. In nature, proanthocyanidins are present in the flowers, leaves, fruits, nuts, seeds, and bark of various plants, protecting them from stress caused by environmental conditions or other living organisms, such as insects, parasitic nematodes, or diseases. More than a thousand derivatives of condensed tannins have been identified, and they have recently attracted increased interest due to their influence on various biological processes [29]. Plants rich in proanthocyanidins have also been used as herbal medicines for mild skin and oral mucosa inflammation and digestion issues [29].  
The total amount of condensed tannins is typically determined from a methanol or acetone extract as an amount of catechchin equivalent (CE) in the dry weight (DW) of the extract. The most common method for determining total condensed tannins is an applied vanillin assay method developed by [PERSON] et al. [30], which is based on the reaction between catechin or proanthocyanidins and vanillin in methanol solution. However, a colourimetric method using 4-dimethylaminocinnamaldehyde hydrochloric acid (DMACA-HCl), developed by [PERSON] et al. [10], is said to have higher sensitivity and specificity compared to a vanillin assay.  
[PERSON] et al. [31] studied the extraction of polyphenic compounds from halophyte biomasses using different solvents and found the concentration of condensed tannins was highest in aqueous fractions or methanol and acetone soluble fractions. As seen from Table 1, the level of proanthocyanidins in halophyte biomasses varies substantially between different species, even those within the same genus. For example, the concentration of proanthocyanidins in _Mesembryanthemum_ species varies between 2.01 \(\pm\) 0.04 mgCE/gDM [32] and 20.3 \(\pm\) 0.98 mgCE/gDM [33], and in _Sueda_ species between 1.21 \(\pm\) 0.05 mgCE/gDM [32] and 15.76 \(\pm\) 1.43 mgCE/g [34]. The highest concentration of proanthocyanidins (118.43 \(\pm\) 11.79 mgCE/gDM), measured from water extract, was found from _Tamarix africana_[31]. For comparison, 17.28 \(\pm\) 1.95 mgCE/gDM of proanthocyanidins were found from _Tamarix gallica_[35] species within the same genus.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Plant Species** & **Solvent** & **Method** & **Concentration** & **Ref.** \\ \hline _Arthrocennium macrostachyum_ & Water & Vanillin assay & 7.50 \(\pm\) 0.80 & [31] \\ \hline _Aster triploium_ & Acetone (80\%) & DMACA-HCl & Not detected & [3] \\ \hline _Cakile martiinum_ & Methanol & Vanillin assay & 14.94 \(\pm\) 0.04 & [37] \\ \hline _Carpobrotus edulis_ & Ethanol & DMACA-HCl & 20.3 \(\pm\) 0.98 & [33] \\ \hline _Cladium mariscus_ & Acetone (80\%) & DMACA-HCl & 38.7 \(\pm\) 2.21 & [3] \\ \hline \hline \end{tabular}
\end{table}
Table 1: The total amount of proanthocyanidins (total condensed tannins) measured from halophyte biomasses. Studies that used a vanillin assay applied the method by [PERSON] et al. [30], except [PERSON] et al. [31], who used the modified method by [PERSON] [36].