ارزیابی تاثیر روش های مختلف خشک کردن بر زمان خشک شدن و برخی خصوصیات فیتوشیمیایی شمعدانی عطری (Pelargonium Graveolens)

خشک کردن یکی از مهم‌ترین فرآیندهای پس از برداشت گیاهان دارویی است. در این پژوهش به‏منظور بررسی تاثیر روش‌های مختلف خشک‌کردن بر گیاه دارویی شمعدانی عطری، آزمایشی بر پایه طرح کاملاً تصادفی با سه تکرار و 12 تیمار اجرا شد. تیمارهای مورد آزمایش شامل خشک کردن در ماکروویو (توان 300، 600 و 900 وات)، خشک کردن در آون (دمای 45، 55 و 65 درجه سانتی گراد)، خشک کردن طبیعی (خشک کردن در سایه محصور اتاق، سایه هوای آزاد، 5 ساعت آفتاب و سپس انتقال به سایه، 10 ساعت آفتاب و سپس انتقال به سایه، و آفتاب کامل) و نمونه گیاهی تازه (به عنوان شاهد) بودند. در روش‌های مختلف خشک کردن، کاهش وزن نمونه ها تا رسیدن محتوای رطوبت به 12 درصد (بر پایه ماده خشک گیاهی) ادامه یافت. نتایج تجزیه واریانس نشان دهنده تاثیر معنی دار روش های مختلف خشک کردن بر زمان خشک کردن، فنل کل، فلاونوئید کل، فعالیت آنتی‌اکسیدانی با دو روش دی‌پی‌پی‌اچ و اف‌آر‌اِی‌پی و محتوای اسانس بود. کم ترین و بیش ترین زمان خشک کردن (4.05 دقیقه و 6 روز) به ترتیب مربوط به تیمارهای خشک کردن با توان 900 وات ماکروویو و خشک کردن در سایه هوای آزاد بود. بالاترین محتوای فنل کل (14.78 میلی گرم گالیک اسید در صد گرم ماده خشک) و فلاونوئید کل (12.83 میلی گرم کوئرستین در صدگرم ماده خشک) به ترتیب در تیمار سایه محصور و سایه هوای آزاد و بیشترین ظرفیت آنتی‌اکسیدانی (1.02=ic50) در نمونه تازه مشاهده گردید. هم چنین گیاهان خشک‌شده در آون با دمای 45 درجه نیز از نظر فنل کل، فلاونوئید کل و فعالیت آنتی‌اکسیدانی غنی بودند. در حالی که نمونه‌های خشک شده در سه توان ماکروویو و نمونه‌های خشک‏شده در آفتاب کامل کم ترین میزان را برای این صفات نشان دادند. بالاترین محتوای اسانس (0.2 درصد وزنی/وزنی بر پایه ماده خشک گیاهی) نیز در تیمار خشک‌‌کردن در آون با دمای 45 درجه مشاهده گردید. به‌طور کلی می‌توان گفت که خشک‌کردن در دماهای بالای آون و توان های بالای ماکروویو باعث کاهش میزان ترکیبات فنولی و فلاونوئید، فعالیت آنتی‌اکسیدانی و درصد اسانس شمعدانی عطری گردید. در حالی‌که روش‌های خشک کردن در سایه محصور، سایه هوای آزاد و آون با دمای 45 درجه، کم‌ترین کاهش را در این صفات نسبت به نمونه گیاه تازه نشان دادند.

Effect of Different Drying Methods on Drying Time and some Phytochemical Characteristic of Pelargonium (Pelargonium graveolens)

Introduction: Drying is one of the most important postharvest techniques for medicinal plants. Pelargonium graveolens (known as geranium) is an important, highvalue perennial, aromatic shrub that can reach a height up to 1.3 m and a lateral growth of 1 m. The essential oil of P. graveolens is extensively used in the perfumery and cosmetic industries. Medicinal plants produce antioxidant compounds, which defend cells against degenerative effects of reactive oxygen species produced during oxidative stress and metabolism. Antioxidants are molecules that scavenge free radicals and reduce/prevent their damages. Therefore, the identification of natural antioxidants as preservative agents plays a pivotal role for the food, cosmetic and pharmaceutical industry. This study was conducted to investigate the effect of different drying methods (microwavedrying, oven drying and ambientdrying) on drying time and some phytochemical properties of P. graveolens.;Material and Methods: In order to evaluate the effect of different drying methods on drying time and some phytochemical properties of Pelargonium, an experiment was conducted at the faculty of agriculture of Lorestan University (Khorramabad, Iran) in 2017. The experiment was carried out based on completely randomized design with 12 treatments and three replications. The drying treatments were microwavedrying (300, 600 and 900 watts), ovendrying (45, 55 and 65 °C), ambientdrying (shadedrying at room, shadedrying in the field, sundrying for five hours and then transfer to the room shade, sundrying for 10 hours and then transfer to the room shade, and sundrying) and fresh samples (as control). In all drying methods, the drying process continued until the moisture content of samples reached to 12% based on dry matter.;Results and Discussion: The results of analysis of variance showed the significant effect of drying methods on total phenol and flavonoids contents, antioxidant activity and essential oil content of the plants. The minimum and maximum of drying time (4.05 min and 6 days, respectively) was related to microwavedrying (900 watts) and shadedrying in the field, respectively. The highest total phenol (14.78 mg GA per 100 g dry matter) and flavonoid (12.83 mg quercetin per 100 g dry matter) contents were observed in plants dried at room shade and field shade, while the highest antioxidant capacity (IC50=1.02) was related to the fresh samples. The plants dried in the oven (45 °C) also had a notable phenol and flavonoid contents with high antioxidant activity. On the contrary, the samples dried in the microwave and sunshine showed the lowest amount of phenol and flavonoid contents and antioxidant activity. The highest essential oil content was obtained from ovendrying at 45 °C (0.2 %w/w based on dry mater), followed by shadedrying in the field (0.17 %w/w based on dry mater), and ovendrying at 55 °C (0.15 %w/w based on dry mater). While, the lowest essential oil content occurred with microwavedrying at 900 W (0.04 w/w based on dry mater). In this study, the amount of essential oil in the microwavedrying plants was significantly reduced by increasing the power of the microwave. The decrease in essential oil content with increasing oven temperature was also observed. The decrease in essential oil content with increasing oven temperature has also been reported in other species such as peppermint, dill, tarragon and sage and could be due to evaporation of the essential oil along with moisture losing during drying process. The results of Hamrouni Sellami et al. (2012) showed that drying in microwave at 800 w increased total phenol and flavonoid levels of sage (Salvia officinalis L.). Their results showed that as the microwave power increased from 600 to 800 watts, the total phenol content increased significantly. In research by Arslan et al., (2010), the lowest total phenol content was observed in the oven dried samples, whereas the highest total phenol content was obtained from the ovenmicrowave treatment and sun drying. The researchers explained that this increase was probably due to the release of phenolic compounds during drying and the reason for the decrease in phenolic compounds in the oven was attributed to the high temperature. Besbes et al., (2004) also reported that with increasing drying temperature, the amount of total phenolic compounds decreases, which may be due to the destructive effect of high temperatures on phenolic compounds. In general, it could be concluded that drying in high temperature of oven and high power of microwave reduces the amount of phenolic and flavonoid compounds, antioxidant activity and essential oil content of P. graveolens. While, shadedrying and ovendrying at 45 °C showed the least reduction in these traits compared to the fresh samples.;Conclusion: It can be concluded that shadedrying at room, shadedrying in the field and ovendrying at 45°C are more suitable for the P. graveolens .While drying treatments in the microwave and sunshine are not suitable for the species. In addition, the results showed that there was a significant relationship between total phenol content and antioxidant activity in both assays.