Screening of a hundred plant extracts as tyrosinase and elastase inhibitors, two enzymatic targets of cosmetic interest

In search for natural products of cosmetic interest, a hundred plant extracts were in vitro tested against elastase and tyrosinase. The inhibitors of these enzymes find application as skin whitening, anti-ageing, anti-wrinkle agents as well as in the treatment of dermatological disorders. Among the tested samples, seventeen extracts resulted strongly active. In particular, eleven out of them were capable to inhibit both enzymes, five showed a strong activity only against tyrosinase and one only against elastase. The IC50 values of the selected samples ranged from 7 to 100 μg/mL and from 20 to 100 μg/mL against elastase and tyrosinase, respectively. Leaves extract of Pistacia lentiscus emerged as the most potent elastase inhibitor and, together with Cytinus hypocistis (aerial parts) and Limonium morisianum (aerial parts), it showed also the lowest IC50 of tyrosinase inhibition. The tested plants were collected in India, Africa and Mediterranean area. Interestingly, among the most active ones, two are endemic and exclusive of Sardinia Island (Italy), namely: Limonium morisianum and Hypericum scruglii, moreover, the latter resulted the only plant which hydroalcoholic extract was capable to inhibit elastase selectively. Moreover, a positive correlation was established among the potency of enzymatic inhibitions and the total phenolic and flavonoid content of the samples. The presence of these aromatic compounds in the most active plants confers them a potential additional value as skin protectors from oxidative damage.