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Abstract: Amorpha fruticosa L. is mainly known as an ornamental plant, but also as the source of the medicinal substance amorphine. Indigo bush is an invasive shrub in the Fabaceae family, native to eastern part of North America. The fruits of this species contain the rotenoid compound amorphine which was used for its cardio-sedative properties in nervous complaints, vegetative neurosis and paroxysmal tachycardia. The present study aims to assess the antimicrobial activity of the essential oil from Amorpha fruticosa fruits in correlation with its chemical composition. The volatile oil was extracted by hydrodistillation (1.3 - 1.8% dry basis) from the fruits of indigo bush, harvested from three locations near Iasi. Gas-chromatography coupled with mass spectrometry was applied in order to analyse the composition of volatile oil, revealing the following main compounds: γ-muurolene, α-zingiberene, δ-cadinene and α-eudesmol. The antimicrobial activity was tested against four Gram-positive bacteria (Staphylococcus aureus, Sarcina lutea, Bacillus cereus, B. subtilis), two Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and against three fungi (Candida albicans, C. glabrata, C. sake). The volatile oil manifested moderate antibacterial activity against Gram-positive bacteria and no antifungal activity that can be explained by the absence of phenolic compounds and the low content of oxygenated monoterpenes.
Key words: Amorpha fruticosa L. fruits, essential oil, GC-MS, antimicrobial activity.
Introduction
Since ancient times, medicinal plants were the basis of remedies used in traditional medicine. They are the source of bioactive compounds that have contributed to the discovery of new therapeutic agents. Increased incidence of infectious diseases and microbial resistance to antibiotics prompted the search and identification of new antimicrobial agents, either natural or synthetic.
Volatile oils have been used since ancient times for their bactericidal, fungicidal, anti-parasitic properties in medicine, food, cosmetics and agriculture. Today, their use in therapy shows an increased interest in terms of safety in administration, lack of side effects, easy acceptance by patients and the health benefits. In addition to uses in drug industry, essential oils are also used as functional ingredients for the foods, beverages and cosmetics. The antimicrobial effects of essential oils vary depending on the species, chemotype, chemical composition and pedoclimatic conditions (Bakkali et al., 2008).
Amorpha fruticosa L. (family Fabaceae, indigo bush) is widely distributed in North America, southern Canada and northern...