Two new biflavanones ( 1 and 2 ), three new bichalconoids ( 3 – 5 ), and 11 known flavonoid analogues ( 6 – 16 ) were isolated from the stem bark extract (CH 3 OH–CH 2 Cl 2 , 7:3, v/v) of Ochna holstii . The structures of the isolated metabolites were elucidated by NMR spectroscopic and mass spectrometric analyses. The crude extract and the isolated metabolites were evaluated for antibacterial activity against Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) as well as for cytotoxicity against the MCF-7 human breast cancer cell line. The crude extract and holstiinone A ( 1 ) exhibited moderate antibacterial activity against B. subtilis with MIC values of 9.1 μg/mL and 14 μM, respectively. The crude extract and lophirone F ( 14 ) showed cytotoxicity against MCF-7 with EC 50 values of 11 μg/mL and 24 μM, respectively. The other isolated metabolites showed no significant antibacterial activities (MIC > 250 μM) and cytotoxicities (EC 50 ≥ 350 μM).

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The leaf extract of Suregada zanzibariensis gave two new modified ent -abietane diterpenoids, zanzibariolides A ( 1 ) and B ( 2 ), and two known triterpenoids, simiarenol ( 3 ) and β-amyrin ( 4 ). The structures of the isolated compounds were elucidated based on NMR and MS data analysis. Single-crystal X-ray diffraction was used to establish the absolute configurations of compounds 1 and 2 . The crude leaf extract inhibited the infectivity of herpes simplex virus 2 (HSV-2, IC 50 11.5 μg/mL) and showed toxicity on African green monkey kidney (GMK AH1) cells at CC 50 52 μg/mL. The isolated compounds 1 – 3 showed no anti-HSV-2 activity and exhibited insignificant toxicity against GMK AH1 cells at ≥100 μM.

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