Cuparane sesquiterpenes from Laurencia natalensis Kylin as inhibitors of alpha-glucosidase, dipeptidyl peptidase IV and xanthine oxidase

The unexplored southern African red marine alga Laurencia natalensis was studied in a search for new enzyme inhibitors. A new cuparane sesquiterpenoid, 8-deoxyalgoane (1) along with two known sesquiterpenoids namely 1-deacetoxyalgoane (2) and algoane (3) were isolated from the MeOH:DCM extract using silica column chromatography with an hexane:EtOAc solvent system. Algoane was obtained as colourless prisms and structures of the three compounds were confirmed by NMR. The three compounds were tested for enzyme inhibitory activities against alpha-glucosidase and dipeptidyl peptidase IV (DPP-IV). Algoane was also tested against xanthine oxidase. In addition, molecular properties were determined to establish drug likeness, and other physico-chemical properties. This is the first report on the chemistry and biological properties of L. natalensis.