Two new ent-kaurane diterpenoids from the leaves of Sphagneticola trilobata

Two new ent-kaurane diterpenoids, namely 3 alpha,16 alpha-dihydroxy-ent-kauran-19-oic acid (1) and 3 alpha,9 beta-dihydroxyent-kauran-19-oic acid (2), together with eight known compounds were isolated and identified from the leaves of Sphagneticola trilobata. Their structures were elucidated on the basis of extensive spectroscopic analysis including 1D, 2D NMR and MS techniques. Known compounds 4, 5 and 8-10 were obtained from S. trilobata for the first time. These compounds were tested for their in vitro alpha-glucosidase inhibitory activity and their tyrosinase inhibitory potential. Compounds 2, 3 and 6 were found to show in vitro alpha-glucosidase inhibitory activity with IC50 values ranging from 0.398 to 0.476 mM, which were close or more potent than reference compound acarbose (IC50 0.410 mM). Compounds 2 and 6 were further revealed to show in vitro tyrosinase inhibitory activity (IC50 29.25 and 40.74 mu M) but inferior to that of the positive control kojic acid (IC50 12.55 mu M).

Automated summary

Two new ent-kaurane diterpenoids were isolated and identified from the leaves of Sphagneticola trilobata, along with eight known compounds. These compounds were tested for their in vitro α-glucosidase inhibitory activity and tyrosinase inhibitory potential. Compound 2, 3, and 6 showed strong α-glucosidase inhibitory activity, and compound 2 and 6 exhibited moderate tyrosinase inhibitory activity.