Anticholinesterase and anti-inflammatory constituents from Caralluma awdeliana, a medicinal plant from Yemen

Abstract

From the dichloromethane (DCM) fraction of the crude ethanolic extract of Caralluma awdeliana, four pregnane glycosides and a flavone glycoside were isolated using a bio-guided isolation approach. The different extracts of C. awdeliana were subjected to in vitro enzyme inhibitory assays of anticholinesterases (AChE and BChE) and anti-inflammatory (COXs and 5-LOX). The highest inhibitory activity was exhibited by DCM fraction against COX-1, COX-2, and 5-LOX with IC₅₀ of 4.8 ± 0.5 μg/mL, 0.68 ± 0.2 μg/mL, and 39.5 ± 3.0 μg/mL, respectively. The DCM showed also a moderate activity against AChE (IC₅₀ 384.72 ± 3.6 μg/mL), and BChE (IC₅₀ 384.72 ± 3.6 μg/mL). The repeated chromatography of DCM fraction resulted in the isolation of two new pregnane glycosides, namely awdeliosides A (1) and B (4), two known ones, namely caratuberosides B and D, along with the known flavone glycoside identified as luteolin 4 -O-neohesperidoside. All the isolated compounds were tested for their in vitro enzyme inhibitory assays. Among the isolated compounds, awdelioside B (4) showed the most potent effect against COX-1 with IC₅₀ value of 10.99 ± 0.35 μM, compared to standard celecoxib (IC₅₀ 230.74 ± 2.62 μM). All the isolated compounds showed weak anticholinesterase, except a moderate activity observed for awdelioside B (4) against BChE with IC₅₀ value of 15.63 ± 3.5 μM, compared to standard donepezil (IC₅₀ 0.77 ± 0.0088 μM).

Keywords: Apocyanaceae; Awdeliosides A and B; Caralluma awdeliana; Caratuberoside B and D; In Vitro Anticholinesterase and anti-inflammatory; Pregnane Glycosides.