stem bark exhibited antimalarial activity by Lactate Dehydrogenase (LDH) assay.

Objectives: The antimalarial drug resistance is an obstacle in the effort to overcome malaria. The new alternative antimalarial drug became in great attention of urgent need. Current antimalarial drugs were derived from plants. Therefore, the plant is considering a potential source of new drugs. belongs to the Hypericaceae family contain xanthones and phenolic compounds, which was reported for their antimalarial activities. This study aims to determine the antimalarial activities of extracts and fractions.

Methods: stem bark (BP14-SB) collected from Balikpapan Botanical Garden in East Kalimantan, Indonesia, was extracted gradually with n-hexane, dichloromethane, and methanol by ultrasonic-assisted extraction method. All extracts were tested against 3D7 by lactate dehydrogenase (LDH) assay and followed by IC determination. The most active extract was further separated and tested for their antimalarial activities.

Results: The results showed that dichloromethane stem bark extract (BP14-SB-D) had the strongest inhibition of parasite growth with the IC value of 0.44 ± 0.05 μg/mL and moderately toxic with the CC value of 29.09 ± 0.05 μg/mL. Further fractionation of BP14-SB-D by open column chromatography using silica gel and gradient hexane-ethyl acetate obtained 12 fractions. LDH assay for these 12 fractions of BP14-SB-D showed that Fraction-6 (IC value of 0.19 ± 0.03 μg/mL) was performed the strongest inhibition of parasite growth, compared to other fractions. TLC identification showed that BP14-SB-D contains xanthone.

Conclusions: The dichloromethane extract of stem bark (BP14-SB-D) and Fraction-6 from this extract exhibited antimalarial activity and the potential to be developed an antimalarial substance.