Two rare antioxidant and anti-inflammatory oleanenes from loop root Asiatic mangrove Rhizophora mucronata

Two oleanenes, olean-18(19)-en-3β-yl-(3,6-dimethyl-3E,6Z-dienoate) and (13α)-27-frido-olean-14(15)-en-(17α)-furanyl-3β-ol representing a class of rare natural pentacyclic triterpenoids were isolated from the chloroform extract of Asiatic mangrove, Rhizophora mucronata Lam. (Family: Rhizophoraceae). The furanyl oleanene exhibited significantly greater antioxidative activities (IC₅₀ 0.73-0.76 mg/mL), than prenylated oleanene (IC₅₀ 0.84-0.96 mg/mL) (P < 0.05). No significant differences in anti-5-lipoxygenase activities of these compounds with the synthetic drug ibuprofen was discernable (IC₅₀ 0.8-0.9 mg/mL), whilst furanyl oleanene demonstrated significantly greater anti-cyclooxygenase-2 (IC₅₀ 0.84 mg/mL) and anti-5-lipoxygenase activities (IC₅₀ 0.78 mg/mL) over prenylated oleanene (IC₅₀ > 0.90 mg/mL). These compounds exhibited lesser activity against cyclooxygenase-1 than cyclooxygenase-2 isoform, and therefore, their selectivity indices remained significantly greater (anti-cyclooxygenase-1_IC50/anti-cyclooxygenase-2_IC50 > 1) than the aspirin (0.02) and ibuprofen (0.44). The lipophilic and steric molecular descriptors were found to occupy a prominent role in determining the bioactivities of the compounds. These previously undescribed oleanenes might serve as potential antioxidative and anti-inflammatory lead molecules in medicinal formulations and food industries.