Sesquiterpenes and monoterpenes from different varieties of guava leaf essential oils and their antioxidant potential

Despite that Sri Lanka is a biodiversity hotspot with numerous guava varieties (Psidium guajava L.), no adequate scientific research has been reported on leaf essential oil (EO) composition based on varieties and its pharmacological properties, namely antioxidant properties. Therefore, this study focused to evaluate the chemical compositions and antioxidative capacity of EOs isolated from leaves of seven guava varieties grown in Sri Lanka, including apple-guava (P. pomiferum, PGA), common-guava (P. guajava, PGCG), two wild-guava; cultivar of P. guajava (PGG) and a cultivar of P. guineense (PGE), two introduced varieties of P. guajava (PGK and PGP), and one introduced variety of P. guineense (PGC). The EOs were isolated using hydro-distillation and the chemical compositions were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) technique, and the compounds that showed greater than 90% matching value were considered for characterization. The yields of EOs ranged from 0.02-0.26% (w/w) where PGE produced the greatest amount. About sixty-eight chemical compounds were identified from seven varieties and Sesquiterpenes were found to be the most abundant in the PGCG, PGG, PGE, and PGA varieties, whereas monoterpenes were found to be the most abundant in PGK, PGP, and PGC varieties. The sesquiterpenes, Nerolidol (70.0–7.9%), (-)-Globulol (21.0–7.0%), and Caryophyllene (20.4–1.4%) and monoterpenes, D-Limonene (30.3–14.1 %) were found as the major compounds of all studied guava varieties. Twenty-eight compounds were identified for the first time in guava EOs, including Cadinadiene-1,4, Benzylacetaldehyde, and Epiglobulol. The antioxidant efficacy of EOs varied from 329.56 ± 2.01 to 85.70 ± 2.01 μL Trolox Eq/L, where PGE showed the highest antioxidative potential. Ultimately, the chemical constituents and antioxidant capacity of isolated EOs varied with the variety, with EO from PGE leaves exerting an amazing antioxidant capacity compared to the others and being rich in Nerolidol. The findings of this study fill the gap in the literature on chemical constituents in the EO of guava leaves, and also it will open the avenue to discover novel potential compounds with outstanding pharmacological activities from guava leaves.