Etude bioguidée des effets de Harungana madagascariensis Lam. et Psorospermum aurantiacum Engl. sur quelques aspects biochimiques du vieillissement cutané

Abstract

Disorders associated with skin aging are of major public health importance worldwide. Strategies to promote healthy aging are therefore recommended and the search of natural products for potential anti-skin aging activity is much needed. Harungana madagascariensis Lam. (HM) and Psorospermum aurantiacum Engl. (PA) are two medicinal plants used by traditional practitioners for skin care. Previous studies have shown the high anti-skin aging potential of these plants. In the present study, crude extracts obtained from a mixture of methylene chloride-methanol (1:1 v/v) of these plants were subjected to bio-guided fractionation and the effect of the isolated fractions on some biochemical factors of skin aging was assessed in vitro. For this purpose, different fractions of each extract were prepared and evaluated for their antioxidant and anti-inflammatory potentials, as well as their capacity to inhibit enzymes involved in skin aging (tyrosinase and elastase) by spectrophotometry. The inhibitory effects of active fractions on melanin biosynthesis genes were analyzed by quantifying the expression of tyrosinase (TYR) and tyrosinase-related protein-1 (TRP-1) genes, as well as their effect on collagen biosynthesis and degradation genes, especially procollagen type-1 (COL1A1) and matrix metalloproteinase-1(MMP-1) on a skin aging model induced by UV-B irradiated cells using a semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). In addition, compounds were purified from the most active fractions and their chemical structures were elucidated from corresponding spectral data. A study of the interactions between the isolated compounds and two target enzymes (elastase and 15-lipoxygenase) were analyzed using molecular docking; and were further confirmed by in vitro spectrophotometry. The hexane fraction of HM (0.350 ± 0.024) showed better antioxidant activities at a concentration of 100 µg/mL than ascorbic acid (0.290 ± 0.009). On the other hand, the PA methanol fraction exhibited the highest DPPH radical scavenging activity with an IC50 of 4.55 ± 0.05 µg/mL compared with ascorbic acid (7.45 ± 0.25 µg/mL). The isolated fractions showed considerable elastase inhibitory activity (greater than 50% inhibition) whereas the hexane fraction of PA showed the highest anti-elastase activity with an IC50 of 15.40 µg/mL. Although all the fractions showed tyrosinase inhibitory activity, the hexane fraction (48 ± 3.02%) of HM showed better tyrosinase inhibition. However, it’s activity was lower than that of standard ascorbic acid (100 ± 0.024%). In addition, the hexane fractions of HM and PA were found to inhibit 15-lipoxygenase with IC50 of 46.80 and 27.55 µg/mL respectively compared to 24.55µg/mL for quercetin, the reference molecule. The hexane fraction of HM exhibited significant (p