Antibacterial, antioxidant, and cytotoxic activities of Syzygium aromaticum (L.) Merr. & Perry essential oil with identification of its chemical constituents

Abstract

Aromatic plants embrace volatile compounds with efficiency in treating different diseases. In Jordan, Syzygium aromaticum flower buds (clove) are extensively used as folk medicine without awareness of its bio-safe dosage. Herein, clove buds were hydrodistilled using the Clevenger apparatus, and the resulting essential oil (CEO) was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). The antibacterial activity was evaluated against tested bacterial strains by agar diffusion test and micro-broth dilution assay. The antioxidant capacity was assessed using DPPH radical scavenging assay, while the cytotoxic potency was unraveled by determination of its anti-proliferative activity against MDA-MB-231 breast adenocarcinoma and normal Vero cell lines. CEO yield was 5.7 ± 1.3% (w/w); encompassed 24 volatile ingredients with eugenol as the principal compound (73.41%). The CEO inhibited the growth of both Gram-positive and Gram-negative bacterial test strains, causing the formation of 13.7 ± 1.5-17.3 ± 0.6 mm and 11.7 ± 1.5-20.7 ± 1.2 mm inhibition zones, respectively with MIC 1.25-5 μL/mL. Moreover, it showed antioxidant activity with IC₅₀ 0.0016 ± 0.0001 μL/mL (1.6 ± 0.1 μg/mL, 2.98 ± 0.4 µg Trolox^®/µg CEO). Intriguingly, the CEO was cytotoxic against both cancerous and noncancerous cell lines at IC₅₀ of 0.25 ± 0.02 μL/mL and 0.18 ± 0.01 μL/mL, respectively. Herein results unveil the potential application of CEO as a pharmaceutical remedy with considering its bio-safe dosage.

Keywords: Syzygium aromaticum; antibacterial activity; antioxidant capacity; clove; cytotoxicity.