Variation in essential oil ratio, total phenolic content, antioxidant and antimicrobial activity of basil as affected by genotype, plant growth stage and daily harvesting time

Basil (Ocimum basilicum L.), which contains many bioactive compounds, is one of the important medicinal and aromatic plants that have been used for various purposes throughout the world since ancient times. The amount, content, and effects of biochemicals synthesized in medicinal and aromatic plants vary significantly depending on several factors. This study was conducted to determine the changes occurred in essential oil ratio, total phenolic content, antioxidant, and antimicrobial activity in basil as a function of genotype, plant growth stage and daily harvest time. In the study with three local basil genotypes, the plants were harvested at the beginning of flowering and at full flowering stages and at three different times of the same day (09:00, 13:00 and 17:00). The essential oil ratio, total phenolic content and antioxidant activity were determined in the extracts prepared from the dried leaf samples of the plants with antimicrobial activity tests performed against 7 bacteria and 2 fungal strains. Essential oil ratio, total phenolic content and antioxidant activity varied significantly among basil genotypes. The effect of plant growth stage (ontogenetic variability) was significant for essential oil content and the effect of daily harvest time (diurnal variability) was significant for total phenolic content. There was a significant positive correlation between total phenolic content and antioxidant capacity. All the basil leaf extracts used in the study showed antimicrobial activity by forming an inhibition zone against all bacterial and fungal strains tested except Pseudomonas aeruginosa. The antimicrobial activity of basil harvested at full flowering was higher than that of basil harvested at the beginning of flowering. According to the results of this study, it can be recommended to harvest basil plants at full flowering for high antioxidant and antimicrobial activity with high essential oil and total phenolic content.