Insights into the chemical composition of Ocimum forskaoliiand O. americanumessential oils and their phytotoxicity

AbstractThe essential oils (EOs) of numerous Ocimumspecies are well-known. The EOs of O. forskaoliiand O. americanumgrowing naturally in Saudi Arabia are compared chemically in the current study. The GC-MS and GC-FID analysis was used for identification and quantitation of EOs’ chemical components, and the chemometric analysis was used to determine the differences between the two species. Additionally, against the weeds Dactyloctenium aegyptiumand Chenopodium murale, the allelopathic potentiality of the two EOs was assessed. Fifty-one compounds were assigned as overall O. forskaoliiEO’ components, with abundance of mono- and sesquit-terpenes (40.49 and 55.15%, respectively). endo-Fenchol (18.15%), tau-cadinol (11.42%), β-atlantol (10.54%), α-eudesmol (7.29%), and α-terpineol (6.94%) were the major components. Sixty-one components were identified via the GC-MS analysis of O. americanumEO, with sesquiterpenes (81.24%) serving as the major class. α-Bulnesene (10.17%), germacrene B (7.72%), endo-borneol (5.51%), isoshyobunone (5.37%), and γ-eudesmol (5.31%) represented the main compounds. Chemometric study showed a distinct difference between the two species’ chemical make-up of the EOs, which might be attributed to genetic changes. The extracted EOs of O. forskaoliiand O. americanumdemonstrated a significant allelopathic effect against the weeds D. aegyptiumand C. murale. Compared to O. americanum, O. forskaoliiEO demonstrated greater allelopathic activity. The main components of each species may be a candidate for the observed allelopathic activity, which may act singularly or in combination.