ABSTRACT

Dissotis rotundifolia is used in traditional herbal medicine for the treatment of diseases and infections such as cough, stomach ache, tooth ache, diarrhoea, painful swellings, jaundice and rheumatism. Hence, this research aims to study the chemical constituents of the leaves of the plant. The air dried and pulverized leaves of Dissotis rotundifolia were extracted with distilled n-hexane and ethylacetate, using Soxhlet apparatus. Isolation and purification were carried out using column and thin layer chromatographic techniques. Fraction B14 gave a single spot on thin layer chromatography with a retention factor (R_f) value of 0.57. Characterization of fraction B14 was done using ¹H-NMR, ¹³C-DEPT, COSY, HSQC and HMBC and pheophytin A was proposed as the structure of the compound. The phytochemical screening revealed the presence of alkaloids (110.23±1.23 mg/100 g), tannins (84.73±1.02 mg/100 g), flavonoids (62.40±0.82 mg/100 g), phenols (95.38±1.74 mg/100 g), saponins (3.39 mg/100 g) and glycosides (55.10 mg/100 g), with alkaloids having the highest concentration and saponins the lowest. The proximate analysis revealed that the moisture, dry matter, crude fibre, crude protein, carbohydrate, ash, lipid content and energy value were 10.62±0.15 %, 89.38±0.15 %, 14.76±0.49 %, 18.42±0.31 %, 44.54±0.28 %, 9.82±0.17 %, 1.84±0.11 % and 268.40±1.17 K Cal. respectively. Vitamins present include ascorbic acid (1.45±0.15 mg/100 g), thiamine (3.10±0.08 mg/100 g), riboflavin (0.18±0.01 mg/100 g), niacin (0.22±0.01 mg/100 g) and β-carotene (which is a precursor of vitamin A) (7.28±0.17 mg/100 g), with β-carotene having the highest concentration and riboflavin the lowest. The mineral elements detected include sodium (63.74±0.05 mg/100 g), potassium (264.60±1.10 mg/100 g), magnesium (63.84±1.71 mg/100 g), calcium (82.60±0.04 mg/100 g), phosphorus (29.42±0.82 mg/100 g), iron (5.18±0.18 mg/100 g), zinc (2.76±0.02 mg/100 g), copper (0.38±0.03 ppm) and lead (0.02±0.01 ppm). The antioxidant activity revealed that pheophytin A and the crude extract showed antioxidant activities of 19.51±0.02 % and 40.23±0.02 % at the highest concentration of 4.00 mg/ml respectively. The antimicrobial activity result of the crude extract at minimum and maximum concentrations of 25.00 and 150 mg/ml revealed growth inhibitions of 4.51±0.09 - 24.04±0.01 mm, 4.00±0.02 - 23.02±0.03 mm and 2.72±0.02 - 15.06±0.15 mm for Escherichia coli, Staphylococcus aureus and Streptococcus pneumoniae respectively. However, Salmonella typhi did not show sensitivity to the extract at 25.00 mg/ml but at 150.00 mg/ml, it gave 20.00±0.52 mm. The Antimycobacterium tuberculosis assay result showed that the crude extract inhibited the growth of the test organism in a dose dependent manner, with the highest growth inhibition of 10.75±0.18 mm at 150 mg/ml and the lowest at 3.62±0.25 mm at 25 mg/ml concentration. This investigation suggests the use of pheophytin A and other bioactive compounds present in Dissotis rotundifolia in pharmaceutical and herbal preparations. The ability of the extract from the leaves of D. rotundifolia to exhibit potent antitubercular activity suggests the use of the plant in the prevention and treatment of tuberculosis. Also the bioactive chemical compounds in the leaves might be responsible for its use in the treatment of various diseases and infections in traditional medicine.