The essential oil composition and antimicrobial activity of leaves of <i>Schistostephium hippifolium</i>

Abstract

The essential oil from the leaves and branches of Schistostephium hippifolium were extracted by hydro-distillation during summer and winter months. Both essential oils were analyzed by gas chromatography- mass spectroscopy (GC-MS) respectively during their extracted period. Fourteen compounds were  identified from essential oil extracted during the February, summer month in South Africa. The volatile oil constituted about 99.31% of the total essential oil composition. The GC-MS reveals the following major constituents in the oil: Chrysanthenyl acetate (32.17%), 1.8-cineole (24.85%), ethanone, 1-  (1-cyclohexen-1-y1) (6.36%), camphor (6.02%), terpinen-4-ol (5.02%), á-pinene (5.13%),  germacrene-D (4.89%) bicyclogermacrene (4.38%), linalool L (2.04%), trans - caryophyllene (1.80%), ã-terpinene (1.95 %). In June, a winter month in South Africa, 48 volatile compounds from the essential oil of S. hippifolium were identified which constituted about 99.99% of the total composition of the  essential oil. The major compounds identified were the 1.8-cineole (18.31%), Germacrene-D (7.43%), bicyclogermacrene (5.24%), 3-cyclohexen-1-ol (6.78%), camphor (5.64%), bicyclogermacrene  (5.24%), á.-pinene (2.52%), â-caryophylle (2.11%), linalool L (3.35%), caryophyllene oxide (1.88%), spathulenol (1.62%) and ã-terpinene (1.39%). In both essential oils (summer and winter), minor volatiles were identified. However, they were in low concentration. The crude extract from the aerial parts of the plant were screened for antibacterial activity against five Gram-positive species  (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Micrococcus kristinae and Staphylococcus faecalis) and five Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Staphlococcus flexneri, Klebsiella pneumonia and Serratiaf marcescens) microorganisms. The minimum inhibitory concentration (MIC) values where highly active at values below two and less active at values above two. All the extracts tested displayed very good activity against both Gram-positive and  Gram-negative bacteria with MIC ranging between 0.098 to 0.65 mg/l.

Key words: Essential oil, GC-MS, oil composition, antimicrobial activity, Schistostephium hippifolium.