Determination of Melatonin and Pharmacological Studies from Mulberry Leaf Extracts

Abstract

Introduction: Mulberry is a plant that widely cultivated in Thailand. Mulberry leaves contain several substances including melatonin and mulberry leaf extract also has a pharmacological effects. This research aim to compare the amount of melatonin in 8 mulberry strains and to study the pharmacological effects of mulberry leaf extract including antioxidant, anti-tyrosinase and anti-inflammatory activity. Materials and method: Mulberry leaves were extracted with methanol. Methanolic extract was purified with solid phase extraction to determine the amount of melatonin with HPLC-Fluorescence detector. In addition, the methanolic extracts were screened pharmacological activities by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, anti-tyrosinase activity assay and nitric oxide inhibition. Results: Fai strain showed the highest level of melatonin (783.99 ng / g dry weight) while Indonesia strain showed the lowest level (83.50 ng/g dry weight). For antioxidant activities, Mhee strain showed the strongest activity (IC₅₀ = 75.86 μg/ml) and the lowest activity was found in Indonesia strain (IC₅₀ = 998.55 μg/ml). Phai-Ubon strain showed the highest anti-tyrosinase activity (% Inhibition = 36.02) at concentration of 100 μg/ml and the lowest activity was found in Mhee strain (% Inhibition = 20.00). For nitric oxide inhibition activities at 20 μg/ml, Mhee strain showed the highest inhibition (78.62%) while Pho strain showed the lowest (46.77%). Conclusion: The different strains of mulberry leaves provide the variety results of melatonin level and some pharmacological activities.