## 4 Bioactive Compounds on Cork and Cork By-Products
### Biological Activity of Cork Extracts and Cork By-Products
\begin{tabular}{l} mg of com- \\ bound/kg of \\ dry cork \\ \end{tabular}  & \begin{tabular}{l} Antioxidant activity \\ (DPPH (IC\({}_{50}\)) = 5.84 \(\pm\) 0.29 \(\mu\)g \\ of extract/mL) \\ \end{tabular}  & \begin{tabular}{l} [80] \\ [80] \\ [25] \\ \end{tabular}  \\ _granulated cork from_ & Caffeic acid (**15**) & 12.9 & \ \begin{tabular}{l} mg of com- \\ bound/kg of \\ dry cork \\ \end{tabular}  & \begin{tabular}{l} Antioxidant activity \\ (DPPH (IC\({}_{50}\)) = 3.58 \(\pm\) 0.20 \(\mu\)g \\ of extract/mL) \\ \end{tabular}  \\ _Portugal_ & p-hydroxybenzoic acid & 1.0 & & & \\  & p-hydroxyphenyllactic & Trace & & \\  & acid (**27**) & & & \\ \hline  & Ellagic acid (**10**) & 1246.46 \(\pm\) 0.18 & & & \\  & Ellagic acid-pentoside & 770.16 \(\pm\) 0.15 & & & \\  & Gallic acid (**12**) & 736.48 \(\pm\) 1.63 & & & \\  & Aesculetin (**24**) & 391.59 \(\pm\) 1.10 & & & \\ methanol/water & Quinic acid (**26**) & 372.86 \(\pm\) 1.94 & & & \\  & Methyl gallate & 251.43 \(\pm\) 0.06 & mg of compound/kg & (DPPH (IC\({}_{50}\)) = 4.77 \(\pm\) 0.02 \(\mu\)g \\ _granulated cork_ & acid & 102.03 \(\pm\) 0.08 & & \\  & Protocatechuic acid (**11**) & 79.26 \(\pm\) 0.10 & & \\  & Ferulic acid (**14**) & Trace & & \\  & Coniferyl aldehyde (**18**) & Trace & & \\  & p-hydroxyphenyllactic & Trace & & \\  & acid (**27**) & & & \\  & Valoneic acid dilactone & 168.01 \(\pm\) 0.70 & & \\  & Caffe acid isoprenyl & 127.98 \(\pm\) 0.28 & & \\  & ester & & \\  & Isorhamnetin- & & & \\  & rhamnoside & Trace & & \\  & Eridictylol & Trace & & \\  & Isorhamnetin & Trace & & \\ \hline  & Ellagic acid (**10**) & 527.59 \(\pm\) 1.70 & & & \\  & Gallic acid (**12**) & 263.04 \(\pm\) 0.52 & & \\  & Aesculetin (**24**) & 176.80 \(\pm\) 0.60 & & \\  & Quinic acid (**26**) & 137.02 \(\pm\) 0.50 & & \\  & Methyl gallate & 96.93 \(\pm\) 0.56 & & \\  & Ellagic acid-pentoside & 46.18 \(\pm\) 0.15 & mg of com- & \\  & Valoneic acid dilactone & 46.05 \(\pm\) 0.11 & & \\  & Protocatechuic acid (**11**) & 16.44 \(\pm\) 0.01 & & \\ _(by-product)_ & Ferulic acid (**14**) & 14.77 \(\pm\) 0.02 & powder & \\  & Coniferyl aldehyde (**18**) & Trace & & \\  & Caffeic acid isoprenyl & 82.47 \(\pm\) 0.29 & & \\  & ester & & \\  & Brevifolin-carboxylic & 53.72 \(\pm\) 0.15 & & \\  & acid & & \\  & Isorhamnetin- & Trace & & \\  & Isorhamnetin & Trace & & \\  & by-hydroxyphenyllactic & Trace & & \\  & acid (**27**) & & \\  & Becivifolin-carboxylic & 102.03 \(\pm\) 0.08 & & \\ _granulated cork_ & acidIn addition to the in vitro studies that already exist and prove the biological activity of these extracts, there is also an in vivo study that proves the tensor and smoothing effect that cork extracts have on human skin [36]. Additionally, due to the presence of these phenolic compounds in cork and its by-products, there is the possibility of incorporating these ingredients in sunscreens, as it has been proven that these compounds, namely lignin [65], can absorb UV radiation. Another known activity of phenolic compounds and flavonoids is the inhibition of tyrosinase in melanocytes by in vitro and in vivo studies [4]; hence, its interest in the development of depigmenting cosmetics is predictable. Thus, correlating the existence of these compounds in cork, namely ellagic (**10**) and gallic (**12**) acids, protocatechuic aldehyde (**17**) and ellagitannins, with their depigmenting activity, one of the possible cosmetic applications of cork is in depigmenting products for the treatment of skin hemishes [4; 79; 91]. Polyphenols can also inhibit the accumulation of lipids in keratinocytes and inhibit the expression of the SREBP-1 gene, which makes them promising in combating acne [92]. A cork hydroglycolic extract has also been studied for this activity, with favourable results [79]. In addition, cork powder has bioabsorbent properties, removing pollutants and oily substances. For this fact, it is being studied for protection of the environment and for the treatment of acne, absorbing the accumulated sebum on the skin [4; 41; 79].