بررسی ویژگی‌های شیمیایی عصاره اتانولی چای سبز و اثر آن بر فعالیت مهارکنندگی و کشندگی آسپرژیلوس نایجر، بوتریتیس سینه‌را و ریزوپوس استولونیفر (عامل فساد میوه توت‌ فرنگی و انگور)

در طول چند دهه گذشته، استفاده از نگهدارنده های طبیعی و عصاره‌های گیاهی به دلیل نگرانی در مورد اثرات نامطلوب بهداشتی احتمالی ناشی از استفاده از نگهدارنده‌های مصنوعی مورد توجه قرار گرفته است. عصاره چای سبز، منبع طبیعی آنتی‌اکسیدان، نه تنها برای افزایش طعم، بلکه برای افزایش ماندگاری محصولات مختلف غذایی مورد استفاده قرار گرفته است. بنابراین، این مطالعه با هدف بررسی فعالیت آنتی‌اکسیدانی و ضد قارچی عصاره چای سبز صورت پذیرفت. برای این منظور، عصاره چای سبز با کمک حلال اتانول استخراج گردید و محتوای فنول کل، فلاونوئید کل، اثر آنتی‌اکسیدانی (بر اساس روش‌های مهار رادیکال آزاد dpph و abts) و فعالیت ضد قارچی آن در برابر سویه‌های قارچی عامل فساد میوه توت‌فرنگی و انگور (آسپرژیلوس نایجر، بوتریتیس سینه‏را و ریزوپوس استولونیفر) مطابق روش‌های دیسک دیفیوژن آگار، چاهک آگار، حداقل غلظت مهارکنندگی و حداقل غلظت کشندگی بررسی گردید. عصاره حاوی mg gae/g 175.60 فنول کل و mg qe/g 47.53 فلاونوئید کل بود و فعالیت مهارکنندگی آن در برابر رادیکال‌های آزاد dpph و abts به‌ترتیب 78.89 و 86.57 درصد بود. نتایج فعالیت ضد قارچی نشان داد که قطر هاله عدم رشد بطور معنی‌داری با افزایش غلظت عصاره افزایش می‌یابد و بوتریتیس سینه‏را و ریزوپوس استولونیفر به‌ترتیب حساس‌ترین و مقاوم‌ترین سویه‌های قارچی نسبت به عصاره بودند. حداقل غلظت کشندگی برای سویه‌های بوتریتیس سینه‏را و ریزوپوس استولونیفر به‌ترتیب 64 و 512 میلی‌گرم در میلی‌لیتر بود. نتایج این مطالعه نشان می‌دهد که عصاره اتانولی چای سبز را می‌توان به منظور افزایش زمان ماندگاری محصولات غذایی استفاده نمود.

investigation of chemical properties of green tea ethanolic extract and its inhibitory and lethal effects on aspergillus niger, botrytis cinerea and rhizopus stolonifer (causing rot in strawberry and grapes)

introductionstrawberry and grapes are generally infected with pathogenic fungi (e.g., aspergillus niger, botrytis cinerea, rhizopus stolonifera, etc.). synthetic fungicides are commonly used as the first line of defense against post-harvest pathogens on packaging lines. however, disposal of toxic waste is a costly process and the hazardous waste causes serious environmental problems. in addition, fungal pathogens have shown a worrying trend of resistance to these fungicides, thus shortening the shelf life of products. compounds that can be equally effective in controlling pathogens, but preventing or minimizing the waste problems will be inevitable. the large volume of internationally processed agricultural products, as well as the increasing demand for organically produced fruits, emphasizes the need to replace synthetic fungicides with safer and biodegradable alternatives. natural plant-derived products effectively meet this criterion and have great potential to influence modern agricultural research. catechins and other polyphenols in green tea show strong antioxidant activity. also, the antimicrobial activity of green tea extract against escherichia coli, pseudomonas aeruginosa, staphylococcus aureus, and candida albicans has been reported. therefore, the present study was performed to prepare the ethanolic extract of green tea and to determine the content of total phenol, total flavonoids, antioxidant activity, and its antifungal effect against aspergillus niger, botrytis cinerea, and rhizopus stolonifer (causing rot in strawberry and grapes). materials and methodsfresh green tea leaves were dried at room temperature and then powdered. then, ethanol (70%) was added to the powdered leaves (solvent to powder ratio of 10:1 v/w) and the mixture was refluxed for 120 min. the resulting mixture was filtered through a filter paper and then concentrated under vacuum and finally dried in an oven.total phenol content (by folin-ciocalteu reagent at 756 nm), total flavonoid content (spectrophotometrically at 510 nm), antioxidant activity (by dpph and abts radical scavenging methods), and antifungal effect (by disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration) of the extract were evaluated. results and discussionthe extract contained 175.60 mg gae /g total phenol and 47.53 mg qe/g total flavonoids and its antioxidant activity using dpph and abts free radical assays was 78.89% and 86.57%, respectively. the results of antifungal activity showed that the diameter of the growth inhibition zone increased significantly with increasing the concentration of the extract, and botrytis cinerea and rhizopus stolonifer were the most sensitive and resistant fungal strains to the extract, respectively. the minimum fungicidal concentrations for the strains of botrytis cinerea and rhizopus stolonifer were 64 and 512 mg/ml, respectively. conclusionthe results of the present study showed that the ethanolic extract of green tea could be considered as potential source of natural antioxidant and antifungal agents. the presence of phenolic and flavonoid compounds may be responsible for the antifungal and antioxidant effects of the extract. however, due to the fact that this study was performed with the crude extract of green tea, it is difficult to identify compounds responsible for antifungal and antioxidant activity. on this point, only the separation of the components of the extract allows the detection of antifungal and antioxidant compounds. this study provides a basis for further researches, in particular the use of these antioxidants and antifungal compounds. green tea extract is especially suitable for products with high sensitivity to lipid oxidation and infection with molds.