Comparative micromorphological study and phytochemical constituents of Stachytarpheta cayennensis (Rich.) Vahl and Stachytarpheta angustifolia (Mill.) Vahl
摘要
Stachytarpheta cayennensis (Rich.) Vahl and Stachytarpheta angustifolia (Mill.) Vahl are two important medicinal plants from the family Verbenaceae. Increasing demand for herbal products from these species necessitates their standardization. The present study aimed to establish comparative histological characters, physicochemical properties, and chemical evaluations of these two closely related species of Stachytarpheta for their identification and standardization as crude drugs. Diagnostic characters unique to S. cayennensis in differentiating the crude drug from S. angustifolia microscopically include glandular trichome with unicellular head, higher stomata number (adaxial- 7.2, abaxial- 17.0), higher stomata index (adaxial- 24.7, abaxial- 39.0), lower stomata size (adaxial- 15.8 by 3.6 µm, abaxial- 16.4 by 4.2 µm), and lower trichome length (adaxial- 255.9 µm, abaxial- 237.5 µm). Physicochemical properties such as lower water-soluble value (1.62 ± 0.59) and ash value (7.02 ± 0.53) with higher extractive values in all the solvents used for S. cayennensis could also serve as a marker tool in distinguishing it from S. angustifolia. Chemical analysis of bioactive compounds yielded higher TPC (2511 ± 3.14 µg gallic/g) and TFC (604 ± 0.5 µg quercetin/g) in S. cayennensis which also corresponds to higher antioxidant activity with IC50 = 127.3 ± 1.72 µg/mL The thin layer chromatography and gas chromatography–mass spectrometry revealed the presence of alkaloids, coumarins, flavonoids, phenolics, steroids, and terpenoids in the methanol crude extract of the species. The unique diagnostic characters, physicochemical properties of the crude drug, and identified compounds from both species may serve as a reference for its identification and standardization which could be included in the West African herbal pharmacopoeia.