In vitro study of the antioxidant, photoprotective, anti-tyrosinase, and anti-urease effects of methanolic extracts from leaves of six Moroccan Lamiaceae

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Six Lamiaceae from Morocco were screened for their antioxidant, photoprotective, anti-tyrosinase, and anti-urease effects in the aim to assess their possible use as a source of bioactive compounds. The amounts of different phenolic compounds were also quantified using calorimetric methods. The highest total phenolic content was recorded with Lavandula pinnata (400.67 ± 3.39 μg GAE/mg), while he uppermost amounts of total flavonoids and condensed tannins were observed with Mentha pulegium (208.31 ± 12.18 µg QE/mg and 43.81 ± 4.07 µg CE/mg, respectively). The strongest antioxidant effect against the DPPH radical was exhibited by Salvia officinalis with an IC50 of 4.33 ± 0.41 µg/mL, which was similar to the value presented by the standard BHA (5.73 ± 0.41 µg/mL) and 5 times less than that obtained with BHT (22.32 ± 1.19 µg/mL). Salvia officinalis also showed remarkable scavenging activity of the radical ABTS with an IC50 of 4.75 ± 0.47 µg/mL, which was slightly higher than those recorded with BHA and BHT (1.81 ± 0.10 and 1.29 ± 0.30 µg/mL, respectively). All the plants gave high values of SPF ranged between 34.66 ± 0.28 and 39.07 ± 1.06. Salvia officinalis presented the best inhibitory effects against tyrosinase and urease with IC50 values of 20.43 ± 1.39 and 10.38 ± 0.10 µg/mL, respectively and was more powerful than kojic acid and thiourea used as standards for each assay, respectively. These results showed the variety of actions exerted by the plants studied, which make them potential candidates as a source of bioactive substances for various applications.