Evaluating biological ethnopharmaceutical activities of fruit and root extracts of Solanum incanum L.

Abstract

Solanum incanum L. is a plant that belongs to the Solanaceae family, growing in tropical climates all over the world. Despite the extensive use of the root and fruit sap extract of S. incanum in the agricultural and ethnopharmaceutical industries in Africa, there is minimal scientific documentation regarding its pesticide bioactive phytochemicals and efficacy. The study investigated the photochemical content (phenolics, flavonoids, saponins, terpenoids and alkaloids) of the methanol, ethyl acetate and hexane crude extracts of the root and fruit of S. incanum. The potential radical scavenging, (antioxidant), cytotoxicity, and efficacy activities of all crude extracts were examined using the 1, 1-diphenyl-2picrylhydrazyl (DPPH), propidium iodide (PI) and aphid leaf dip (ALD) assays respectively. The total phenolic, alkaloid, flavonoid, terpenoid and saponin content were highest in the methanol fruit (MFE), (3.49 ± 1.16 mg GAE/100 mg), steroidal fruit (SAE), (0.14±0.06 mg ATP/100 mg, hexane fruit (HFE), 3.62±1.23 mg QCT/100 mg, hexane root (Hroot), (1.19±0.47 mg LIN/100 mg and saponin (3.74±1.17 mg/100 mg). The aqueous extract of the ethyl acetate fruit had the highest antioxidant activity with an IC50 of 35.53±0.53 μg·mL-1 (p < 0.05) The methanol fruit and steroidal alkaloid extracts exhibited potent cytotoxicity against Vero cells demonstrating the highest cell mortality rate of 98% and 70% respectively at 100 μg·mL-1. Melphalan which was used as a positive control had a mortality rate of 75% cell at 100 μg/mL concentration. The methanol fruit extract exhibited the highest efficacy against the cabbage aphids with an LD50 of 13.16±3.78 μg·mL-1 (p < 0.05). The results indicated that the fruit and root of S. incanum have a variety of phytochemicals that may be considered for use as antioxidants and/or pesticides. By exhibiting the most potent cytotoxic activity against Vero cells, S. incanum roots have the greatest potential for the discovery of cytotoxic compounds necessary to develop anticancer drugs. The extracts with high potent efficacy against cabbage aphids need to be investigated further as pesticides to benefit the disadvantaged communities in the Southern African region. Key words: Antioxidant, cytotoxicity, lethal dose, mortality rate, phytochemicals, quantitative analysis