In vitro evaluation of Syzygium aromaticum L. ethanol extract as biocontrol agent against postharvest tomato and potato diseases

Abstract

E thanolic extract of dried flower bud of Syzygium aromaticum L. (clove) was investigated to evaluate its antifungal activity against local fungal isolates causing postharvest infections form potato and tomato. Four fungal isolates; Geotrichum candidum, Alternaria alternata, Fusarium oxysporum and Mucor hiemalis were identified. All fungal isolates were found to be inhibited by the extract; whereas the smallest inhibition zone) of S. aromaticum extract was 2.5% for M. hiemalis, A. alternata, G. candidum and 12.5% for F. oxysporum. Quantitative assessment of phytochemical compounds in clove plant revealed the presence of phenolic acids (20.80%); flavonoids (26.81%); tannins (4.90%), saponins (2.60%), alkaloids (1.60%), total protein (17.83%), total carbohydrate (2.23%) and total oil (0.90%). Biochemical profile was revealed by GC/MS which detect 18 different chemical compounds. The major compounds were eugenol (17.27%), trans-caryophyllene (0.50%), humulene (3.33%), anthracenedione (3.35%), cedran-diol (0.61%), citroflex A (5.45%) and lucenin 2 (8.25%). TLC technique and different solvent systems were employed to select the proper one based on its capacity to isolate the maximum number of fluorescent spots in crude extract.Chloroform-acetone-butanol (CAB) 85:15:20 could efficiently separate three bands (A, B and C). Each detected band was individually screened for its antifungal activity against the isolated fungi. Only band C showed a significant antifungal activity. Mass spectroscopy (MS) was used to investigate characteristics, purity as well as expectation of both chemical formula and molecular weight of the isolated compounds; which finally proved that glucoside β-sitosterol was the main compound represented in fraction -C.