Phytochemical Screening, In-vitro Antimicrobial Activity and Antioxidant Characteristics of Tetrapleura tetraptera Extracts

Aims: In order to provide scientific evidence for the ethno-medical claims, this study was conducted to determine the phyto-constituents, antimicrobial activity and the antioxidant activity of the crude leaf and stem bark extracts of Tetrapleura tetraptera (Schum. & Thonn.) Taub.

Study Design: The plant was authenticated by a taxonomist at Forest Research Institute of Nigeria (FRIN) and a voucher specimen was kept for future reference. The leaf and stem bark were extracted using 95% ethanol and the crude extracts were screened for phytochemicals, antimicrobial and antioxidant potentials and then fractionated.

Place and Duration of Study: The study was undertaken between October 2015 and June 2016, at Nigeria Institute of Leather and Science Technology (Microbiology Laboratory) Zaria, Kaduna State and the Chemistry Advanced Research Centre, Sheda Science and Technology Complex, Sheda, Abuja, Nigeria.

Methodology: Air-dried leaves and stem bark of T. tetraptera were pulverized to powder with a mortar and a pestle. The powdered leaves and stem bark were then kept in airtight containers until required for further work. Each of the ground plant samples (1 Kg) was exhaustively extracted with 95% ethanol using a Soxhlet extractor. The extracts were concentrated at 40°C to dryness using a rotary evaporator to obtain the crude extracts. The crude extracts were screened for phytochemicals and antimicrobial activity against some selected pathogens such as Staphylococcus aureus, Streptococcus pneumonia, Streptococcus pyogenes, Corynebacteruim ulcerans, Candida albicans, Candida tropicalis, Klebsiclla pneumonia, Candida krusei and antioxidant activity using standard procedures.

Results: Alkaloids, phlobatanins, flavonoids, volatile oils and tanins were present in the crude extract of each plant part. However, steroids and saponins were detected only in the stem bark while phenols, resin and terpenoids were detected only in the leaf extract. The antioxidant activity of the extracts was determined by the DPPH inhibition method. The crude stem bark extract exhibited a stronger free radical scavenging activity than the leaf (69.81: 63.46% at 5 mg/ml and 71.54: 63.85% at 4 mg/ml, respectively). The results of antimicrobial screening also showed that the crude stem bark extract was more active with inhibitory activity between 27-32 mm compared to that of the crude leaf extract which was between 24-29 mm, against the test organisms, Staphylococcus aureus, Streptococcus pneumonia, Streptococcus pyrogens, Klebsciella pneumonia, and Candida krusei. The minimum inhibitory concentration (MIC) of the crude stem bark extract was recorded at 0.625 mg/ml, while that of the leaf was between 0.625 and 1.25 mg/ml. The results obtained suggested that both the crude ethanol extracts of the stem bark and leaf possess strong anti-bacterial and anti-fungal activities.

Conclusion: The susceptibility of microorganisms such as Staphylococcus sp. and Klebsiella sp. to certain phyto-compounds infers that the bioactive compounds in plants can be further developed for the management of several disease conditions thereby authenticating their use in traditional medicine. The relative potency of the studied plant extracts in comparison to the standard drug ciprofloxacin suggests that possible new drug candidates can be harnessed from the plant, Tetrapleura tetraptera. From the results obtained in this study, further work will now be done to isolate and identify the active principles.