CHEMICAL CONSTITUENTS, ANTIMICROBIAL AND ANTIOXIDANT ACTIVITIES OF SELECTED SAPINDACEAE PLANTS

Abstract

Blighia sapida (Bs), Lecaniodiscus cupanioides (Lc) and Paullinia pinnata (Pp) (family Sapindaceae) are ethno-medicinal plants used as antimicrobial and antioxidant agents in the treatment of fevers, skin infections, dysentery and coughs. However, the information on chemical constituents and Essential Oils (EOs) from parts of these plants is limited and the bioactive compounds responsible for their activities have not been fully explored. This study was therefore, designed to extract, isolate and characterise bioactive constituents from these three plants. The plants Bs, Lc and Pp were collected in Ibadan and authenticated at the University of Ibadan Herbarium as UIH–22407, UIH–23138 and UIH–23139, respectively. The EOs from the plants parts were obtained by hydro-distillation and analysed by Gas Chromatography (GC) and GC-Mass Spectrometry. Hexane, ethylacetate and methanol were used to obtain root extracts of Bs. The active ethylacetate fraction was subjected to chromatographic techniques. The isolated compound from Bs was characterised using spectroscopic methods. The EOs and compound isolated were subjected to antimicrobial assay following standard protocols using bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella pneumonia) and fungi (Candida albicans, Aspergillus niger, Rhizopus stolonifer, Penicillium notatum) with gentamicin and tioconazole as standards, respectively. Antioxidant activity was done using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay with α-tocopherol, butylated hydroxyanisole and ascorbic acid as standards. Data were analysed using descriptive statistics. The yield of EOs from the three plants ranged from 0.3 to 5.6%. Total of 197, 153 and 142 compounds were identified from Bs, Lc and Pp, respectively. Major constituents of the EOs were α-ionone, pentadecanal, geosmin, verticiol, α–caryophyllene and (Z)-11-octadecenoic acid for Bs; (E)-2-hexenal, 4-hexyl-2,5-dihydro-2,5-dioxo-3-furanacetic acid, tetrapentacontane and 1,2,3,5,7-pentamethyl-1H-pyrrolo [2,3-f] quinolin-9-ol for Lc; caryophyllene and caryophyllene oxide for Pp. However, hexahydrofarnesyl acetone was the most commonly present at 71.4%, 50.0% and 75.0% of EOs from Bs, Lc and Pp, respectively. Infrared absorptions of the compound from Bs at 3331 cm-1 (O-H) and 1701 cm-1 (C=O); proton NMR signals (ppm) at δ 7.90 (1H, d), 6.23 (1H, d), 7.22 (1H, s), 6.80 (1H, s) and 3.82 (3H, s); carbon-13 NMR with ten carbons (CH3, 4CH2, 5C) ; molecular ion at m/z 192.05 corresponded to 7-hydroxy-6-methoxy-chromen-2-one. Zone of inhibition (mm) of Bs, Lc, Pp EOs and 7-hydroxy-6-methoxy-chromen-2-one at 3.13-100.00 mg/mL ranged from 10±0 to 26±0, 10±0 to 28±0, 10±0 to 28.0±1.0 and 10±0 to 26±0, respectively, while standards ranged from 26±0 to 40±0 mm at 10 µg/mL. The IC50 of EOs in antioxidant activity ranged from 0.981 to 1.047 µg/mL, while that of the isolated compound was 1.027 µg/mL compared to 0.950-1.023 µg/mL for standards. Bioactivities of the essential oils of Blighia sapida, Lecaniodiscus cupanioides, Paullinia pinnata and newly isolated 7-hydroxy-6-methoxy-chromen-2-one from Blighia sapida supported the use of the plants in ethno-medicine for treatment of microbial infections.