Croton oligandrus Pierre & Hutch (Euphorbiaceae) Extracts and Isolated Compounds Reverse HIV-1 Latency

Croton oligandrus Pierre & Hutch is a tropical tree that grows in West and Central Africa, used in ethnomedicine to treat cancer, diabetes, headaches, convulsions, urinary diseases, and inflammatory diseases. As other Croton species have been observed to possess chemical compounds that target HIV latency-reversal, we hypothesized that this species may have similar properties.

The identification of extracts and compounds of this species, which have HIV-1 latency-reversing activity in J-Lat T cell lines.

The stem bark was obtained, air-dried, powdered, and extracted using dichloromethane. In vitro flow cytometry was used to monitor GFP expression, a marker of HIV latency reversal, following treatment of J-Lat T cells with extracts and compounds.

Four extracts were found to reverse HIV latency, the most active extract showing better activity (ie, latency reversal in 69.7 ± 7.1% [mean ± s.e.m.] of J-Lat 10.6 cells at 1 µg/mL) than control agents prostratin (46.2 ± 9.5% at 1.2 µg.mL) and the "Mukungulu" (Croton megalobotrys) extract (34.9 ± 24.2% at 1 µg/mL). Extracts reversed HIV latency through mechanisms over and above protein kinase C (PKC) activation and distinct from histone deacetylase (HDAC) inhibition. The most active extract also synergized with the control HDAC inhibitor romidepsin but did not synergize with other extracts. Isolated compounds (β-Stigmasterol and lupeol) had limited but consistent latency reversal on their own.

The plant extracts and compounds reverse HIV latency through mechanisms additional to PKC activation and/or synergize with romidepsin in vitro. Extracts and compounds from this plant may enhance the activity of current HIV latency-reversing agents being assessed in HIV cure studies.