Evaluation of antibacterial and antioxidant activity of Aloe vera ( Aloe barbadensis Miller ) gel powder using different solvents

The present study was planned to investigate the phytochemical compounds present in Aloe vera and antimicrobial and antioxidant activity of Aloe vera gel powder with different solvents. The phytochemical compounds were screened qualitatively and glycosides, flavonoids, tannins, phenols, saponins, proteins, triterpeniods gave positive results while alkaloids and phlobatannin gave negative results. The polyphenol and flavonoid contents and antioxidant activity of Aloe vera gel powder extract using three different solvents (ethanol, methanol, acetone) were analyzed. The ethanolic extract showed maximum polyphenol (28.44 ± 2.67 mg GAE/g), flavonoid (63.90± 2.39 mg CE/g) and DPPH radical scavenging activity (51.09±0.33%). Antibacterial activity of extracts was examined by agar diffusion method with four microbial species (Salmonella typhi, Escherchia coli, Bacillus subtilis and Staphylococcus aureus). Maximum antibacterial activity was observed in ethanol extract of Aloe vera gel powder. Hence, Aloe vera gel powder can be used as an antimicrobial and antioxidant agent in food preservation and to prevent diseases related to oxidative stress.


Introduction
Aloe vera has been used in ancient cultures of India, Egypt, Greece, Rome and China for its medicinal value for several thousand years.It was known as plant of immortality in biblical times by the Egyptians and believed to be effective for wound healing, for antiinflammatory effect, for radiation injury, to treat gastrointestinal problems, skin diseases and as an anti-ulcer and anti-diabetes.The Aloe vera is derived from the Arabic word "Alloeh" which mean bitter substance and also known as first aid plant or burn plant [1].In the food industry, it has been considered as an important ingredient in functional foods and health drinks, beverages and curd [2, 3].Aloe vera is considered as curative agent mainly due to presence of transparent and soft tissue inside the leaf.The polysaccharides present in Aloe vera extracts are responsible for health benefits [4,5].Aloe vera gel has many biological activities including its antimicrobial activity, antidiabetic effects, antioxidant

Total phenolic assay
The reagent Folin-Ciocaltue was used to measure total phenolic content of the extracts [15].In, 0.5 ml of extracts, 2.5 ml of Folin-Ciocalteu's phenolic reagent was added.After 5 min at room temperature 2.5 ml of 7.5% sodium carbonate solution was added and allowed to incubate for 90 min at room temperature and absorbance was determined at 765 nm with UV-VIS spectrophotometer.Total phenolic content of samples was expressed as milligram of gallic acid equivalents (GAE)/g dry weight.

Total flavonoids assay
The method used to determine the total flavonoids in Aloe vera sample was Aluminium Chloride (AlCl3) colorimetric assay [16].In 10 ml volumetric flask which have 4 ml of H2O, 1 ml of extract was added and after 5 min 10% AlCl3 and after one min, 2 ml of 1M NaOH was mixed and total volume was made upto 10 ml with H2O.The absorbance of mixture was measured using UV-VIS spectrophotometer at 510 nm.Total flavonoid content of samples was expressed as mg catechin equivalents (CE)/g dry sample.The bacterial test organisms i-e gram positive (Bacillus Subtilis, Staphylococcus Aureus) and gram negative (Salmonella Typhi, Eschersia Coli) were inoculated at the nutrient agar medium using sterile cotton buds and incubated at 37 o C for 24 hrs.The diameter of inhibition zones was measured in millimetre.

Screening of phytochemical components
The present studies revealed that Aloe vera gel powder contain important phytochemical compounds.The presences of active phytochemicals were qualitatively analyzed and results are shown in (Table 1).Glycosides, flavonoids, tannins, phenols and spanions were found to be present in the studied sample while phlobatannins and alkaloids were found absent.Presence of mono-and polysaccharides, saponins, tannins, organic acids, sterols, enzymes, various vitamins and minerals in Aloe vera were confirmed in a previous study [19]

t control Conclusion
From the present study, it was concluded that Aloe vera gel powder contain some important medicinal compounds and ethanolic extract showed more total polyphenol, total flavonoid, antioxidant capacity and antibacterial activity as compared to methanolic and acetone extract.The ethanolic extract of Aloe gel powder showed highest antibacterial activity on Bacillus subtilis and Staphylococcus aureus while acetone extract showed maximum antibacterial activity against Salmonella typhi.So, Aloe vera gel powder is valuable to be used in food, cosmetics and medicines.
Antioxidant activity of methanolic, ethanolic and acetone extracts were analyzed by DPPH (2,2-diphenyl-1-picrylhydrozyl) method [17].In 3 ml of extract, 0.1 mM of DPPH solution was added and kept in dark place for 30 min at room temperature and absorbance was measured at 517 nm on a UV-VIS spectrophotometer.The antioxidant activity was calculated by using the following formula: Antioxidant activity (%) = [(AC -AE) /AC] x Where AC = absorbance of a DPPH solution without extract AE = absorbance of the tested extract Antibacterial activity of Aloe vera The antibacterial activity of Aloe vera was determined by disc diffusion technique [18].

Graph 1 .
Antibacterial activity of Aloe vera gel powder extract using ethanol, methanol and acetone solvent w.r.