OCCURRENCE OF MICROPLASTICS IN SURFACE SEDIMENTS OF BEACHES IN LAGOS, NIGERIA

IN VITRO ANTIOXIDANT AND ANTIMICROBIAL POTENTIALS OF THREE EXTRACTS OF AMARANTHUS HYBRIDUS L. LEAF AND THEIR PHYTOCHEMICALS

Medicinal plants are valuable natural sources for the development of potentially safe drugs. The biological activities associated with these plants are due to the presence of certain phytochemicals that act individually or synergistically. Thus, this study examined the phytochemical components, antioxidant and antimicrobial activities of n-hexane, ethylacetate and methanolic extracts of Pennisetum purpureum (Schumach). Qualitative and quantitative phytochemical assays of P. purpureum showed the presence of alkaloids (0.004%), saponins (0.002%), flavonoids (0.021%), steroids, terpenoids and glycosides (0.008%). Methanol, n-hexane and ethylacetate extracts of P. purpureum were examined for antimicrobial activity using the disc diffusion method. Six microbial strains were exposed to six different concentrations of each extracts; 200 mg/ml, 100 mg/ml, 50 mg/ml, 25 mg/ml, 12.5 mg/ml and 6.25 mg/ml. The three extracts demonstrated varied concentration-dependent antimicrobial activities against the test organisms. The methanolic extract showed antibacterial activity against E. coli, S. aureus, B. cereus and antifungal activity against T. mentagrophyte and A. niger. Among all extracts, the methanolic extract of P. purpureum exhibited relatively strong antifungal activity against A. niger (10.3±0.12 mm) when compared to the standard antifungal agent, fluconazole (13.9±0.12 mm). Furthermore, antioxidant activities were spectrophotometrically studied using vitamin C as standard; methanol and ethylacetate extracts of P. purpureum showed pronounced scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH); and had a potent reductive ability on ferric ion and phosphomolybdate. However, only the non-polar extract of P. purpureum showed a non-significant correlation and significant differences when compared to vitamin C. Antioxidant activities of the plant extracts were observed in the order of methanol >ethylacetate> n-hexane extracts. The results showed that P. purpureum contains phytochemicals that significantly contributed to the observed antimicrobial and antioxidant abilities of the plant and could be used as a potential source for the development of novel therapeutic drugs.

Chromatographic separation of methanolic extract of Baphia nitida heartwood gave two crystalline solids characterized as 3,9-dimethoxy-6aR,11aR-dihydro-6H-benzofuro(3,2-C)[1]benzopyran (also known as homopterocarpin) with molecular formula C ₁₇ H ₁₆ O ₄ (1.57% yield) and 2,4-dimethoxybenzaldehyde C ₉ H ₁₀ O ₃ (2.27% yield). Each of the isolated compounds showed a single spot on developed thin layer chromatographic plate under ultra-violet light (254 nm) and spray reagent (10% sulfuric acid in methanol solution). Structural elucidation was achieved using Fourier transform infrared (FT-IR) spectroscopy, one and two-dimension nuclear magnetic resonance (NMR) techniques. Distortionless enhancement by polarization transfer-edited-heteronuclear single quantum coherence (DEPT-ed-HSQC) was also a useful tool that aided the characterization of the two secondary metabolites isolated from Baphia nitida heartwood.

The concentrations of polychlorinated biphenyls (PCBs) in sediment samples from the New Calabar River in the Niger Delta Region of Nigeria were determined. Grab sediment samples were collected from five stations in the river and analyzed for individual PCB congeners using gas chromatography - mass spectrometer. The Σ ₈ PCB (sum of eight congeners) identified in the samples ranged from 0.21 to 2.16 mg/kg. Congener 105 and 194 were the most and least abundant with 34.65 % and 2.46 % respectively. The lower chlorinated congeners (below PCB 101) were prominent with 54.68 % of the total PCBs concentration in the sediments. The results of this study should make PCBs contaminants of grave concern in the Niger Delta Region.