Nutritional, phytochemical, and antimicrobial properties of Senna siamea leaves

Senna siamea is a medicinal plant with numerous benefits in different parts of the world. This study evaluated the leaf's nutritional composition, mineral composition, phytochemical constituents, antioxidant properties and antimicrobial properties, and high-performance liquid chromatography (HPLC) using standard methods. The proximate analysis revealed the presence of moisture content (12.14 ± 0.01), ash content (1.05 ± 0.07), crude fat (4.21 ± 0.10), crude protein at (9.78 ± 0.11), crude fiber (2.70 ± 0.32), and carbohydrate content (70.12 ± 0.37). Mineral analysis showed an abundance of potassium (125.18 ± 0.04), followed by magnesium (32.62 ± 0.01), and phosphorus (18.30 ± 0.02). The phytochemical screening revealed the presence of saponins, flavonoids, phenolics, steroids, and alkaloids with 13.25 ± 0.03 mg GAE/g total phenolics and 3.99 ± 0.01 mg QE/g flavonoid contents, respectively. IC₅₀ values of the scavenging abilities of DPPH, NO radicals, and TBARS were 206.01 µg/mL, 347.66 µg/mL, and 394.92 µg/mL, respectively while the IC₅₀ value for FRAP was 145.01 µg/mL. Salmonella typhimurium 14028 and Pseudomonas aeruginosa 27853 were most susceptible. At 100 mg/mL, their average zone of inhibition was 18 and 16 mm for ethyl acetate and 15 and 12 mm for methanol, respectively. The minimum inhibitory concentration (MIC) for both isolates was 25 and 50 mg/mL while the leaves were rich in chlorogenic acid, p-coumaric acid, friedelin, quercetin, emodin, cassiarin A, and kaempferol. These results reveal the leaf as a good source of nutrients and also confirm its phenolic antioxidant activity and antimicrobial properties.