Effect of Drying Methods and Type of Packaging Materials on Phytochemical Content and Total Antioxidant Capacity of Five Medicinal Plants with Cosmetic Potential over Three Months Storage at Ambient Temperature

Abstract

Drying and storage are the most integral parts of the post-harvest practices of herbal materials. These practices directly influence the physical and chemical quality of the processed product. Therefore, the main objective of the present study was to analyze the effect of drying methods and packaging materials on total flavonoid content, total phenolic content, and total antioxidant capacity of five medicinal plant leaves with cosmetic potential. Leaves of Hibiscus rosa-sinensis L., Senna alata (L.) Roxb., Centella asiatica (L.) Urb., Ocimum tenuiflorum L. and Justicia adhatoda L. were dried to a constant weight using shade drier at 30-35°C, solar drier at 30-40°C and oven at 40°C. Thereafter, dried leaves were stored using three different packaging materials namely glass jars, polythene bags and gunny bags at ambient temperature for three months. Aluminum chloride colorimetric assay, folin-ciocalteau method, and phosphomolybdate assay were employed to analyze the total flavonoid content (TFC), total phenolic content (TPC) and total antioxidant capacity (TAC) of ethanolic extracts of leaves respectively in each month. Data were presented as mean ± standard deviation of minimum three replications. Significant interactions of the drying methods and packaging materials on TAC, TFC and TPC of dried leaf materials were analyzed using Two-way ANOVA. Results showed that the maximum TFC, TPC and TAC in oven dried H. rosa-sinensis (23.48±2.49 mg RE/100g DW, 1.09±0.24 mg GAE/100g DW and 0.39±0.05 mg AAE/100g DW respectively) and C. asiatica (128.64±10.59 mg RE/100g DW, 2.38±0.32 mg GAE/100g DW and 2.2±0.05 mg AAE/100g DW respectively) leaves stored in glass jars and solar dried S. alata (117.43±9.00 mg RE/100g DW, 3.99±0.29 mg GAE/100g DW and 1.07±0.04 mg AAE/100g DW respectively), O. tenuiflorum (216.02±0.75 mg RE/100g DW, 1.92±0.12 mg GAE/100g DW and 1.07±0.03 mg AAE/100g DW respectively) and J. adhatoda (11.13±1.23 mg RE/100g DW, 1.02±0.19 mg GAE/100g DW and 0.42±0.04 mg AAE/100g DW respectively) leaves stored in glass jars at the end of the storage period. However, statistically significant interaction (p value < 0.05) was not reported between drying method and packaging material on TPC of C. asiatica and O. tenuiflorum leaves and TFC of S. alata leaves. In conclusion, determining the effect of different processing methods on chemical constituents of aforementioned plant leaf materials is suggested to assure the quality of the final product.