Comparative testing of antimicrobial activity of aqueous extracts of Aloe vera and Lycium barbarium

Abstract

Plants have a very important role in natural medicine because of their composition rich in vitamins, minerals, antimicrobial and immunomodulatory compounds. Since antibioresistance to some antibiotics used in current therapy in human medicine and veterinary medicine is nowadays a major problem, researches have searched for alternative methods of replacement or combination of antibiotics with different plant extracts with antimicrobial and/or immunomodulatory effect. This experiment was designed to evaluate the comparative antimicrobial effect of aqueous extracts of aloe (Aloe vera) and goji berries (Lycium barbarum) on some species of bacteria and fungi. We used for this experiment five kinds of aqueous extracts of aloe vera (two extracted from the for six months old plant, two from a 4 years old plants and a standard commercially available aqueous extract). Five types of aqueous extracts of goji fruit (1/1 goji soak, total aqueous extract, fruit centrifuged supernatant, fruits supernatant filtered through 0.2μm Millipore and watery sediment from plant mortar) were also tested. Four kinds of microorganisms including Gram-positive bacteria (Staphylococcus aureus ATCC 6538P), Gram-negative bacteria (Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 27853) and fungi (Candida albicans ATCC 10231) were used for determining the sensitivity. Testing was done by disc diffusion method with some changes according to the tested compounds. The interpretation of disk diffusion test revealed that Aloe vera extracts had inhibitory effect only on the strains of Staphylococcus aureus ATCC 6538P, the effect being stronger for total extract (100%) as well as for standardized extract. The growth of Escherichia coli ATCC 10536 strain, was increased instead of being inhibited. On Candida albicans ATCC 10231 strain, only standardized extract had a good inhibitory effect. Regarding the antimicrobial effect of aqueous extracts of goji fruit we found a weak inhibitory effect, however, observing a strong inhibitory effect on E. coli strain. This study demonstrated that aqueous extracts of aloe and goji have antimicrobial effect, which depends on the concentration of the extract and the type of microorganism tested. The results can represent a prospect into the use of these extracts as substitutes for antibiotics or along with antibiotics and may have practical applications in medicine, cosmetics and food industry.