Phenolic Profile, Antioxidant and Enzyme Inhibitory Activities of Leaves from Two Cassia and Two Senna Species

Abstract

Several species within the genera <i>Cassia</i> or <i>Senna</i> have a treasure of traditional medicines worldwide and can be a promising source of bioactive molecules. The objective of the present study was to evaluate the phenolic content and antioxidant and enzyme inhibition activities of leaf methanolic extracts of <i>C. fistula</i> L., <i>C. grandis</i> L., <i>S. alexandrina</i> Mill., and <i>S. italica</i> Mill. The two <i>Cassia</i> spp. contained higher total polyphenolic content (42.23-49.75 mg GAE/g) than the two <i>Senna</i> spp., and <i>C. fistula</i> had significantly (<i>p</i> ˂ 0.05) the highest concentration. On the other hand, the <i>Senna</i> spp. showed higher total flavonoid content (41.47-59.24 mg rutin equivalent per g of extract) than that found in the two <i>Cassia</i> spp., and <i>S. alexandrina</i> significantly (<i>p</i> ˂ 0.05) accumulated the highest amount. HPLC-MS/MS analysis of 38 selected bioactive compounds showed that the majority of compounds were identified in the four species, but with sharp variations in their concentrations. <i>C. fistula</i> was dominated by epicatechin (8928.75 µg/g), <i>C. grandis</i> by kaempferol-3-glucoside (47,360.04 µg/g), while rutin was the major compound in <i>S. italica</i> (17,285.02 µg/g) and <i>S. alexandrina</i> (6381.85). The methanolic extracts of the two <i>Cassia</i> species exerted significantly (<i>p</i> ˂ 0.05) higher antiradical activity, metal reducing capacity, and total antioxidant activity than that recorded from the two <i>Senna</i> species' methanolic extracts, and <i>C. fistula</i> displayed significantly (<i>p</i> ˂ 0.05) the highest values. <i>C. grandis</i> significantly (<i>p</i> ˂ 0.05) exhibited the highest metal chelating power. The results of the enzyme inhibition activity showed that the four species possessed anti-AChE activity, and the highest value, but not significantly (<i>p</i> ≥ 0.05) different from those obtained by the two <i>Cassia</i> spp., was exerted by <i>S</i>. <i>alexandrina</i>. The <i>Cassia</i> spp. exhibited significantly (<i>p</i> ˂ 0.05) higher anti-BChE and anti-Tyr properties than the <i>Senna</i> spp., and <i>C. grandise</i> revealed significantly (<i>p</i> ˂ 0.05) the highest values. <i>C. grandise</i> revealed significantly (<i>p</i> ˂ 0.05) the highest α- amylase inhibition, while the four species had more or less the same effect against the α-glucosidase enzyme. Multivariate analysis and in silico studies showed that many of the identified phenols may play key roles as antioxidant and enzyme inhibitory properties. Thus, these <i>Cassia</i> and <i>Senna</i> species could be a promising source of natural bioactive agents with beneficial effects for human health.