Chemical Compositions, Antioxidant and Antimicrobial Potential of Butterfly Pea (Clerodendrum volubile) Leaves

Abstract

Butterfly pea (Clerodendrum volubile) leaves known as Ewe-marugbo or dagba is popular among the Ilaje/Ikale people of Ondo state, Nigeria. The dark green leaf is usually blended with other spices to make the popular local soup called m’arugbo, which is used to eat their favorite swallow delicacy called Pupuru. The locals ascribe claims to the intake of the leaf like purgative, anti-malarial and the cleansing of the stomach/womb of new mothers making it easy for them to excrete without having cause to force out the faeces. Leaves of C. volubile were freshly plucked at the flowering stage. The leaves were manually cleansed, dried under shade at ambient temperature (25 ± 2) °C till a constant weight was reached and the dried leaves were milled to powder. The proximate, phytochemical, mineral, antioxidants and antimicrobial properties of fresh and air-dryed leaves; aqueous, acetone and ethanolic extracts of Clerodendrum volubile leaves were studied. Proximate compositions of C. volubile showed differences between fresh and air-dryed butterfly pea leaves. The results showed that the percentage (%) moisture, protein, fats, ash, crude fibre and carbohydrate contents of the fresh butterfly pea leaves on dry weight basis are 57.21, 4.33, 5.23, 3.10, 15.43 and 14.70 respectively; while that of the air-dryed butterfly pea leaves are 3.81, 10.00, 12.50, 8.74, 34.81 and 30.14, respectively.The mineral composition of the samples showed that the fresh and air-dryed samples of butterfly pea leaves contain considerable amount of minerals but low amount of zinc (0.02-0.05 mg/100 g). Calcium (7.06 mg/100 g) was the predominant mineral among the macro-minerals determined in the fresh butterfly pea sample followed by potassium (3.87 mg/100 g), magnesium (1.24 mg/100 g), sodium (0.42 mg/100 g), iron (0.10 mg/100 g) and zinc (0.02 mg/100 g); while Potassium content (14.18 mg/100 g) of the air-dryed butterfly pea sample was observed to be highest among the macro-minerals followed by calcium (9.78 mg/100 g), magnesium (2.30 mg/100 g), sodium (0.80 mg/100 g), iron (0.18 mg/100 g) and zinc (0.05 mg/100 g). Nickel content in the fresh butterfly pea sample (0.001-0.003 mg/100 g) is the least followed by the copper content (0.004-0.02 mg/100 g).The phytochemical analysis of the butterfly pea sample recorded highest in saponin content (3600.00 mg/100 g), followed by phytate (1730.40 mg/100 g), oxalate (279.10 mg/100 g), tannin (9.00 mg/100 g) and alkaloid (4.12 mg/100 g).The antioxidant assay result showed that ethanolic extract is highest in total phenol, FRAP, DPPH and ABTS (1731.34 mg/100 g, 1114.09 mg/100 g, 42.91% and 1.36% respectively) while acetone extract is highest in ascorbic acid and total flavonoid (8250 mg/100 g and 2000.00 mg/100 g respectively). Acqeous extract had the least antioxidant activity.Five pathogenic bacteria (Salmonella typhii, Shigella dysenteriae, Staphylococcus aureus, Bacillus cereus and Escherichia coli) and two fungi Aspergillus flavus and Aspergillus niger,were used to test for the antimicrobial potential of ethanolic, acetone and acqeous extracts of butterfly pea leaves. At 1 mg/ml ethanolic extract showed significant zones of inhibition against all test organisms (Bacillus cereus 23 mm, Shigella dysenteriae 20 mm, Staphylococcus aureus 19 mm, Escherichia coli 15 mm, Aspergillus flavus 23 mm and Aspergillus niger 17 mm) except with Salmonella typhii a gram negative bacteria; acetone extract was able to inhibit the growth of Escherichia coli 20 mm,Bacillus cereus 15 mm,Aspergillus flavus 12 mm and Aspergillus niger 12 mm; while the aqueous extract was able to inhibit the growth of three test bacteria (Bacillus cereus 24 mm, Escherichia coli 20 mm and Shigella dysenteriae 18 mm). From these results, it can be deduced that leaves of C. volubile is food with high crude fibre whose claim about ease of bowel evacuation can be said to be possible; also the ethanolic extract of butterfly pea leaves was found to exhibit higher antioxidant and antimicrobial activity than both acetone and aqueous extracts.