The human immunodeficiency virus (HIV) infection and the associated acquired immune deficiency syndrome (AIDS) remain global challenges even after decades of successful treatment, with eastern and southern Africa still bearing the highest burden of disease. Following a thorough computational study, we report top 10 phytochemicals isolated from Croton dichogamus as potent reverse transcriptase inhibitors. The pentacyclic triterpenoid, aleuritolic acid (L12) has displayed best docking pose with binding energy of -8.48 kcal/mol and Ki of 0.61 μM making it superior in binding efficiency when compared to all docked compounds including the FDA-approved drugs. Other phytochemicals such as crotoxide A, crothalimene A, crotodichogamoin B and crotonolide E have also displayed strong binding energies. These compounds could further be investigated as potential antiretroviral medication.

African Trypanosomiasis is a neglected tropical disease with a large impact on the livelihood of the rural poor in Sub-Saharan Africa. The available drugs for managing this disease are old, expensive and are facing the problem of drug resistance. Thus, the aim of this study was to evaluate in vivo antitrypanosomal efficacy of aqueous and absolute methanol leaf extracts of Verbascum sinaiticum Benth. against Trypanosoma congolense field isolate. Verbascum sinaiticum (Local name ‘qetetina’) is a biennial plant, and 60–150 cm tall. It is traditionally used to treat wound, stomachache, viral infection, cancer, sunstroke, fever, abdominal colic, diarrhea, hemorrhage, anthrax, and hepatitis. The efficacy of aqueous and absolute methanol leaf extracts of V. sinaiticum was evaluated in a randomized experiment with Swiss albino mice infected with T. congolense field isolate. The extracts were administered at doses of 100, 200 and 400 mg/kg by intraperitoneal injection for seven days at 12 Days Post-Infection (DPI) when the peak parasitaemia level was approximately 108 trypanosomes/ml. Parasitaemia, Packed Cell Volume (PCV), mean survival time and change in body weight were used as indices for monitoring the efficacy of the extracts. Diminazene (28 mg/kg) was used as a positive control while 2 % Tween was used as the negative control. Phytochemicals screening were conducted following standard methods. The extracts showed no toxicity effect in Swiss albino mice and had LD50 above 2000 mg/kg. The phytochemicals screened in V. sinaiticum were alkaloids, flavonoids, glycoside, saponins, steroids, phenolic compounds, and tannins. The mice treated with absolute methanol leaf extract of V. sinaiticum at 400 mg/kg dose had significantly lower mean parasitaemia (7.20 ± 0.16) (p < 0.001) as compared to the negative control group (8.82 ± 0.12) on day 14 of treatment. Animals treated with the same dose had significant (p < 0.001) higher PCV value and body weight and as well as the highest mean survival time of 40.20 ± 0.31 days as compared to the negative control at the end of the observation period. This study established that Verbascum sinaiticum had trypanocidal activity. The crude extracts have partially eliminated trypanosomes in a dose-dependent manner. The study can be a basis for future in-depth analysis of the biologically active chemicals.

Introduction: Human immunodeficiency virus (HIV) affects the body’s defense mechanisms and leads to a number of opportunistic infections which later cause fatality as a result of an acquired immunodeficiency syndrome (AIDS). More than half a million individuals have lost their life in 2020 due to this disease. Antiretroviral drugs have played a great role in improving the quality of life of HIV infected individuals. The side effects of these drugs coupled with resistance of the virus to the various regimens, necessitates the search for potentially new and effective antiretroviral medication. The objective of this study is to evaluate anti-HIV activity of crude extracts of three Croton plants. Methods: As part of our effort in screening anti-HIV medications, we evaluated the cytotoxicity and anti-HIV activity of three Croton species used as herbal medicine in Africa. Crude extracts of Croton macrostachyus, Croton megalocarpus and Croton dichogamus were tested for their replication inhibition activity against laboratory adapted strains HIV-1_IIIB in Human T-lymphocytic MT-4 cell line. Results: Based on our findings, the crude aerial part extract of C. dichogamus displayed the highest anti-HIV activity by inhibiting 73.74% of viral induced cytopathic effect (CPE) at IC₅₀ value of 0.001 + 0.00 μg/mL giving a selectivity index (SI) of 3116.0. In addition, the crude leaf extract of C. megalocarpus showed higher anti-HIV activity by inhibiting 74.65% of CPE at IC₅₀ value of 0.05 + 0.03 μg/mL giving an SI of 571.3. Conclusion: Out of five extracts from three Croton species screened for anti-HIV activity using human T-lymphocytic MT-4 cells, the leaf extract of Croton megalocarpus and aerial part extract of Croton dichogamus could be considered as promising extracts as they display high antiviral activity with low toxicity and high selectivity index values. To investigate the active constituents responsible for the anti-HIV activity, chemical identification of the active constituents is now in progress in our laboratory. Since there is no previously reported anti-HIV activity for these plants, there is a great need to isolate the compounds responsible for the noted activity.

Croton macrostachyus is an important plant in traditional African medicine, widely utilized to treat a variety of diseases. In Kenya, HIV-infected patients use leaf and root decoctions of the plant as a cure for cough, back pain, bleeding, skin diseases, warts, pneumonia, and wounds. This study aimed to evaluate the anti-HIV activities and cytotoxic effects of extracts and chemical constituents isolated from C. macrostachyus. In our previous study we demonstrated that the hexane, CH₂Cl₂, ethyl acetate and methanol soluble fractions of a 1:1 v/v/ CH₂Cl₂/MeOH crude extracts of the leaves and stem bark of C. macrostachyus exhibited potent anti-HIV activities against HIV-1 with IC₅₀ values ranging from 0.02–8.1 μg/mL and cytotoxicity effects against MT-4 cells ranging from IC₅₀ = 0.58–174 μg/mL. Hence, hexane soluble extract of 1:1 v/v/ CH₂Cl₂/MeOH crude extract of the leaves of C. macrostachyus, that was more potent against HIV-1 at IC₅₀ = 0.02 μg/mL was subjected to column chromatography leading to the isolation of 2-methoxy benzyl benzoate (1), lupenone (2), lupeol acetate (3), betulin (4), lupeol (5), sitosterol (6) and stigmasterol (7). Lupenone (2), lupeol acetate (3) and betulin (4) exhibited anti-HIV-1 inhibition at IC₅₀ = 4.7 nM, 4.3 and 4.5 μg/mL respectively. The results obtained from this study support the potential of C. macrostachyus, as a source of anti-HIV constituents.

In recent years, elucidation of novel anti-HIV bioactive compounds from natural products is gaining importance rapidly, not only from the research and publications, but also from controlled clinical studies. Here we report three new anti-HIV eudesmane-type sesquiterpenes, 5β-Hydroxy-8α-methoxy eudesm-7(11)-en-12,8-olide (1), 5β,8α-Dihydroxy eudesm-7(11)-en-12,8-olide (2) and 5β-Hydroxy-8H-β-eudesm-7(11)-en-12,8-olide (3). These are trivially named ermiasolide A-C and were isolated from the bark of Croton megalocarpus. 5β-Hydroxy-8α-methoxy eudesm-7(11)-en-12,8-olide (1), showed the highest anti-HIV activity by inhibiting 93% of the viral replication with an IC₅₀ = 0.002 µg/mL. On the other hand, 5β-Hydroxy-8H-β-eudesm-7(11)-en-12,8-olide (3) and 5β,8α-dihydroxy eudesm-7(11)-en-12,8-olide (2), inhibited viral replication by 77.5% at IC₅₀ = 0.04 µg/mL and 69.5% at IC₅₀ = 0.002 µg/mL, respectively. Molecular docking studies showed that the proposed mechanism of action leading to these results is through the inhibition of HIV-protease.

An anti-HIV methanol-soluble fraction of a 1:1 CH₂Cl₂:CH₃OH extract of twigs of a Kenyan Croton dichogamus yielded seven compounds, the new crotocascarin ω (1), the known β-oplopanone (2), dihydroconiferyl acetate (3), 3’(4’’-hydroxyphenyl)-propyl benzoate (4), lupeol, sitosterol and stigmasterol. Crotocascarin ω (90%) inhibited HIV-1 replication with an IC₅₀ value of 5.3 nM, and the compound was cytotoxic towards MT-4 cells presenting an IC₅₀ value of 84 µM. In silico modelling showed that the anti-HIV activity for compound 1 could be through the HIV-1 protease inhibition. Graphical Abstract