Abstract
A new clerodane diterpene, named 6α-hydroxy-3,13E-clerodien-15-oic acid (1), together with a known clerodane diterpene (2), four known labdane diterpenes (3–6), a triterpenoid (7), a known steroid (8), and two benzenoid compounds (9 and 10) were isolated from Detarium microcarpum Guill. & Perr. The structures of all obtained compounds were determined by chemical properties and spectroscopic evidence, accompanied by comparisons with data in the literature. Electronic circular dichroism (ECD) was performed for compounds 1–4 to confirm the absolute configuration. Compounds 1–3 and 8–10 were evaluated for the protective effect on osteoblasts. Compound 1 was observed to increase the proliferation of dexamethasone (DEX)-treated MC3T3-E1 cells significantly at 1 μM, which was comparable with the positive control geniposide at 10 μM. The results were further confirmed by flow cytometry analysis. In addition, compound 1 increased the level of alkaline phosphatase (ALP) and mineralization in osteoblasts inhibited by DEX. Moreover, Compound 9 (vanillic acid) showed a pronounced inhibition (IC50 6.5 ± 0.6 μM) on reactive oxygen species (ROS) production, and 10 (4-O-methyl gallic acid) showed a good inhibition with IC50 as 103.3 ± 2.2 μM, compared with the standard drug ibuprofen (IC50 54.2 ± 9.2 μM). Besides, compounds 1–3 and 8–10 were non-cytotoxic against MCF-7, NCI-H460, Hela, and BJ cell lines.
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•Ten secondary metabolites were isolated from Detarium microcarpum Guill. & Perr.•6α-hydroxy-3,13E-clerodien-15-oic acid (1) is a new clerodane diterpene.•ECD was performed for compounds 1–4 to confirm the absolute configuration.•Compound 1 protected DEX-treated MC3T3-E1 cells more significantly than geniposide.•Effect of 1 was confirmed by flow cytometry, ALP, and mineralization analysis.•Vanillic acid showed a more pronounced inhibition of ROS than ibuprofen.