First report of a lactonic disecosteroid from the buccinid gastropod Babylonia spirata

A lactonic steroid with an unprecedented 1, 10: 8, 9-disecoergostane framework was identified from the ethyl acetate-methanol extract of buccinid gastropod mollusk, Babylonia spirata collected from the southwestern coast of Indian peninsular region. The compound was characterized as 1, 10: 8, 9-disecoergosta-8-en-A-homo-6a-oxa-1-one by exhaustive spectroscopic methods including two-dimensional nuclear magnetic resonance and mass spectroscopic investigations. The disecosteroid displayed moderate carbolytic enzyme inhibition activity as distinguished by its inhibitive effects against alpha-amylase and alpha-glucosidase (IC50 0.40 and 0.54 mg/mL, respectively). The anti-inflammatory (5-lipoxidase inhibitory) activity of the titled secondary metabolite was found to be superior (IC50 < 0.85 mg/mL) than the commercial anti-inflammatory drug (ibuprofen IC50 > 0.85 mg/mL). However, significantly greater antioxidant property was recorded for the studied disecosteroid as evaluated by in vitro 2, 2-diphenyl-1-picrylhydrazyl radical inhibition potential (IC50 0.30 mg/mL) than that of standard, alpha-tocopherol (IC50 > 0.50 mg/mL). The in silico molecular docking studies were conducted to explain the anti-5-lipoxidase and anti-alpha-amylase properties of the isolated compound. The molecular binding interactions of the ligands with the pro-inflammatory 5-lipoxidase and the carbolytic enzyme alpha-amylase, demonstrated that their binding energies/docking scores were positively associated with their in vitro bioactivities. A plausible pathway for the biosynthetic origin of lactonic disecosteroid in B. spirata was proposed from an ergosterol precursor. Structure-activity correlation study demonstrated that the biological activities of the disecosteroid were directly proportional to their electronic properties allied with lesser steric restrictions.