CHEMICAL COMPOSITION, ANTIOXIDANT CAPACITY AND ANTIBACTERIAL ACTIVITIES OF THREE SPECIES OF KOLANUTS

Abstract

Kolanut is a member of the tropical family sterculiaceace. It is a native stimulant which is commonly chewed in many West African cultures. The objective of this study is to evaluate the chemical composition, phytochemical screening, antioxidant capacity and anti-bacterial activity of three species of kolanuts (Cola acuminata, Cola afzelii and Cola nitida). Five varieties of kolanuts were collected from a local farm in Orin Ekiti. Nuts removed from the husks, dried and powdered. Three types of extraction were carried out (acetone, cold and hot aqueous extraction). Proximate, mineral and phytochemical were determined using standard analytical methods. Antioxidant activity was determined by Ferric reducing antioxidant power (FRAP), 2,2-Diphenyl 1-Picrylhydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) methods, caffeine and theobromine were evaluated by spectrophotometric and titration methods respectively. Antibacterial screening was done using agar well diffusion method. The results showed that red cola acuminata has the highest content of moisture (10.54%) crude protein (10.11%), crude fat (2.70%), ash (4.96%) and crude fiber (7.60%) and the least carbohydrate (64.09%). White cola nitida has the highest calcium (951.56mg/100g), magnesium (48.14 mg/100g), and iron (1.85 mg/100g). Heavy metals like chromium, lead and nickel were not detected in all the samples but cadmium was detected in all the samples except red Cola nitilda in a very low concentration, range from 0.019 mg/100g to 0.42 mg/100g. The phytochemical analysis revealed the presence of saponin, tannin, flavonoid, steroid, terpenoid, alkaloids and cardiac glycoside in all the samples. Phlobatannin and anthraquinone were not detected. The quantitative result of the phytochemical analysis showed that red Cola acuminata has the highest value of flavonoid (12.969 mg/g), phenol (8.023 mg/g), saponin (37.136 mg/g), terpenoid (12.979 mg/g), tannin (7.977 mg/g), steriod (3.573 mg/g) and glycosides (16.238 mg/g) but the underutilized Cola afzelii has the highest alkaloid content (47.125%), Cola afzelii showed the highest content of the antioxidant activity in FRAP, DPPH and ABTS. White Cola acuminate and Cola afzeli have the highest caffeine content 1.128  g/ml and red Cola nitida has the least caffeine content 1.04  g/ml. The bromine contents were the same in all the samples (0.72%) except red Cola acuminata (0.54%). The antibacterial activity showed that in cold water extract, Cola afzelii showed the highest zone of inhibition (10.0 mm) on E. coli. Hot water extract of red Cola acuminata showed the highest inhibition zone of 8 mm on shigella. Acetone extract showed the highest zone of inhibition (9.0 mm) from Cola afzelii on shigella and white Cola acuminata on B. subtilis. Maximum zone of inhibition for the standard was on P. aeruginosa and P. mirabilis (18.0 mm) and the minimum inhibition was on S. aureus (10.0 mm). The results obtained indicate that these three species of kolanuts pose promising chemotherapeutic and antibacterial potentials. Key words: Cola nitida, Cola acuminata, Cola afzelli, Phytochemical analysis, Antioxidant, Antibacterial.