Avocado Seed Extracts as Natural Antimicrobial and Antioxidant: Phytochemical Analysis and Bioactivity Studies

The growing campaign for the consumption of crude extracts of avocado seed has necessitated numerous studies to validate the claims of their effectiveness in herbal treatment. Also, the nuisance that the seeds of avocado constitute when discarded into the environment calls for a creative way to convert the waste into a useful resource. This research focused on the analysis of the phytochemical content of avocado seed, the sensitivity of bacteria and fungi to the crude extract of the seed, as well as the antioxidant potential of the seed. Avocado seed was extracted with ethyl acetate via microwave-assisted extraction. The test for the presence of secondary metabolites revealed that alkaloids, anthraquinone, saponins, glycosides, phlobatannins, flavonoids, coumarins, triterpenes and steroids were present in the avocado seed ethyl acetate extract (AEE). Staphylococcus aureus, Bacillus subtilis, Vancomycin-resistant enterococci (VRE), Escherichia coli, Proteus mirabilis, Candida albicans and Candida tropicalis, were sensitive to AEE, with Escherichia coli and Proteus mirabilis being the most sensitive (25 mm inhibition zone) for bacteria, while Candida albicans was the most sensitive (24 mm inhibition zone) for fungi. The minimum inhibitory concentration (MIC) for all the test organisms was 2.5 mg/mL. The minimum bactericidal/fungicidal concentration (MBC/MFC) ranged from 5 mg/mL to 10 mg/mL. Bacillus subtilis, VRE, and Candida tropicalis showed MBC/MFC at 10 mg/mL, while Staphylococcus aureus, Escherichia coli, Proteus mirabilis and Candida albicans showed MBC/MFC at 5 mg/mL. The antioxidant potential of AEE which was a measure of its ability to inhibit DPPH radicals increased with increase in concentration from 27.0 6% at 100 µg/mL to 40.69 % at 400 µg/mL, with IC50 value lower than 100 µg/mL which suggests that AEE possesses meaningful antioxidant potential within a moderate range.