Phytochemical investigation of the fruits of Schisandra chinensis led to the isolation of 13 lignans including schisandrene (13), a new lignan based on a dibenzocyclooctadiene backbone with an exocyclic double bond. Its structure and absolute configuration were established using NMR, MS, and CD data. Antioxidant activity of the lignans was evaluated using a DCFH-DA cellular-based assay. The structure-activity relationships of the dibenzocyclooctadiene lignans showed that the exocyclic methylene functionality was essential for antioxidant activity, with the benzoyloxy group probably enhancing such effects.

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The dichloromethane-methanol (1/1) extract of the stem bark of Turraeanthus africanus (Meliaceae) showed remarkable antimicrobial activity against Cryptococcus neoformans, Staphylococcus aureus and methicillin-resistant S. aureus. Phytochemical investigation of this extract afforded six new diterpenoid derivatives, (+)-16-acetoxy-12,15-epoxylabda-8(17),12,14-triene ( 3), [16( E),12 S,15 R]-16-acetoxy-12,15-epoxy-15-isopropoxy- ent-labda-8(17),13(16)-diene (turraeanin A, 4), [16( E),12 R,15 S]-16-acetoxy-12,15-epoxy-15-isopropoxy- ent-labda-8(17),13(16)-diene (turraeanin B, 5), [16( E),12 S,15 R]-16-acetoxy-12,15-epoxy-15-methoxy- ent-labda-8(17),13(16)-diene (turraeanin C, 6), [16( E),12 R,15 S]-16-acetoxy-12,15-epoxy-15-methoxy- ent-labda-8(17),13(16)-diene (turraeanin D, 7) and (12 S,13 S,15 R)-12,15-epoxy-15-methoxy- ent-labd-8(17)-en-16-al (turraeanin E, 9) together with the known compounds, 15,16-epoxy- ent-labda-8(17),13(16),14-triene ( 1), (+)-pumiloxide ( 2), ent-labda-8(17),12 ( E)-diene-15,16-dial ( 8) and 16-acetoxy-12( R),15-epoxy-15beta-hydroxylabda-8(17),13 (16)-diene ( 10). Compound 10 was obtained as its acetoxy derivative ( 10a) and compound 11 was the product of hydrolysis of 6. Antimicrobial activity of the isolates was assayed and compounds 8, 9, 10a and 11 exhibited significant activities.

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