Cytotoxicity and anti-HIV activities of extracts of the twigs of Croton dichogamus Pax

BACKGROUND: Acquired immunodeficiency syndrome (AIDS) is a clinical syndrome resulting from infection with human immunodeficiency virus (HIV), which causes profound immunosuppression. Anti-HIV drugs that are currently available are chemically synthesized and are frequently limited by side effects, the emergence of drug resistance, affordability, and availability, with over 5 million people in the world lacking access to treatment. As a result, to discover new anti-HIV agents, we investigated the effects of Kenyan C. dichogamus extracts on the laboratory-adapted strain HIV-1IIIB in human T-lymphocytic MT-4 cells. METHODS: Four soluble fractions of 1:1 v/v CH₂Cl₂:MeOH extract of the twigs of C. dichogamus Pax were tested for their replication inhibition activity against the laboratory-adapted strain HIV-1IIIB in the human T-lymphocytic MT-4 cell line. The plant extracts were further evaluated for their cytotoxicity in MT-4 cells using the MTT assay. RESULTS: The cytotoxicity CC₅₀ values of the methanol and methylene chloride soluble fractions of C. dichogamus were found to be between 19.58 ± 0.79 and 167 ± 0.8 µg/ml, respectively. The hexane, methylene chloride, and methanol soluble fractions of the 1:1 v/v CH₂Cl₂:MeOH extract of the twigs of C. dichogamus showed inhibition of the HIV-1IIIB laboratory-adapted strain in a virus-infected cell culture antiviral assay. The methanol soluble fraction of the 1:1 v/v CH₂Cl₂:MeOH extract of the twigs of C. dichogamus showed significant anti-HIV activity by inhibiting more than 90% of viral-induced cytopathic effects with an IC₅₀ value of 0.06 ± 0.01 µg/ml, giving an SI of 318.5. CONCLUSION: Based on our findings, the methanol soluble fraction of the 1:1 v/v CH₂Cl₂:MeOH extract of the twigs of C. dichogamus has shown potential efficacy in inhibiting viral replication and could be considered a promising candidate for further studies.