Proximate, Phytochemicals and Gas Chromatography Flame Ionization Detection (GC-FID) Profiling of Ethanolic Extract of Guava (Psidium Guajava) Leaves and Its Antimicrobial Activities on Some Bacterial Isolates.

This study examined the proximate, phytochemicals and antimicrobial properties of extract of Psidium guajava (guava) leaves against some bacterial isolates. Samples of guava leaves were collected, washed, dried, pulverized, and then subjected to ethanolic extraction and concentrated using rotary evaporator. The proximate, vitamins and phytochemicals were determined by standard methods. The bioactive compounds were further quantified using gas chromatography flame ionization detector (GC-FID) techniques. The minerals were determined using atomic absorption spectrophotometer (AAS). Using the diffusion technique with agar wells, some bacteria isolates were examined for their susceptibility to the extract. The proximate composition (%) showed that protein content was 18.73, ash (3.63), moisture (8.24), and carbohydrate (66.01). The physicochemical revealed that the temperature was 27.63oC, pH (5.97), total solids (0.98), solids-non-fat (0.37), and specific gravity (0.73) with the titrable acidity content value as 0.32. The vitamin content (mg/100g) of the extract indicated that the value of vitamin B was 5.78, B1 (4.77), B6 (6.63), C (6.37), while the carotenoids was 5.67 mg/100g. The sodium (ppm), calcium (ppm), and phosphorous (mg/kg) content of the sample were 34.68, 6.06 and 7.79, respectively. Phytochemicals revealed moderate level of alkaloids, saponins etc., while glycosides was high. The GC-FID revealed the presence of twelve (12) bioactive constituents: lunamarin being the most abundant with a concentration of 33.6262 ppm, while kaempferol (0.3564 µg/ml) was the least. At 200 mg/ml, the extract showed higher activity and varying zones of inhibition (mm) at 17, 8, 20, and 9 on E. coli, Shigella sp., Lactobacillus sp and Staphylococcus aureus. The minimum inhibitory concentration (MIC) of the sample against E. coli and Lactobacillus sp, was at 50, while Shigella sp and Staphylococcus aureus was at 200. This study revealed that guava leaves are rich sources of health promising nutrients and some bioactive compounds that are inhibitory against some pathogens.