Antiprotozoal screening of the Cuban native plant Scutellaria havanensis

Scutellaria havanensis Jacq. (Lamiaceae) is a native medicinal herb with a history of use in Cuba.

This study screens the antiprotozoal activity of S. havanensis.

Chloroform and methanol extracts from leaves and stems were evaluated in vitro at doses between 0.015 and 200 μg/mL against protozoan parasites: Plasmodium berghei, Trichomonas vaginalis and Leishmania amazonensis. Chloroform and methanol extracts were characterized by GC/MS. Cytotoxicity against mouse peritoneal macrophages was tested in parallel.

Scutellaria havanensis extracts exhibited IC₅₀ values between 7.7 and 32.2 μg/mL against trophozoites of P. berghei and T. vaginalis; while the extracts were inactive against L. amazonensis promastigotes. Trichomonicidal activity of methanol extract exhibited the best selectivity but chloroform extract showed the highest antiplasmodial, trichomonicidal and cytotoxic activity. The majority of compounds in the chloroform extract were hydroxy and/or methoxyflavones (77.96%), in particular, wogonin (48.27%). In methanol extract, wogonin (5.89%) was detected. Trichomonicidal effect of wogonin was moderate (IC₅₀=56 μM) and unspecific with respect to macrophages (SI = 2). On the contrary, antiplasmodial activity of wogonin were particularly active (IC₅₀=15 μM) demonstrating a higher selectivity index (SI = 7.4).

Wogonin is an active principle compound of the chloroform extract of S. havanensis against P. berghei and T. vaginalis trophozoites, whereas the methanol extract of S. havanensis should be investigated more deeply as a trichomonicide. Our findings suggest that wogonin is potentially useful for the development of antimalarial alternative treatments.