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The objectives of this current study were to determine the varying contents of vitamin C, chlorophyll, total phenolic compounds in White mugwort (Artemisia lactiflora) which were tested under different types of organic fertilizer. Completely randomized design with four treatments (applications of no fertilizer, cow, chicken and bat manures) was assigned for the field experiments at Department of Medicinal Plant Science, Faculty of Agricultural Production, Maejo University in Chiang Mai, Thailand. The results showed that the sampled plants with chicken manure application yielded the highest fresh (31.00±1.00 g FW/plant) and dried weights (3.20±0.20 g DW/plant). Furthermore, plants with chicken manure treatment also gave the highest chlorophyll content of 0.93 mg/g FW. Whereas, the highest levels of vitamin C (1.35 mg/100g FW) and total phenolic compounds (4.84 mgGAE/g DW) were found in plants with cow manure treatment.

Orthosiphon aristatus (Blume) Miq. tea is a traditional herbal tea in Thailand. This herb is used to prevent and treat a wide range of diseases such as diuresis, hypertension, and diabetes. In this study, three different drying temperatures used for herbal tea processing were evaluated (40, 50, and 60 °C) for their secondary metabolites [total phenolic content (TPC), caffeic acid (CA), rosmarinic acid (RA), and total flavonoid content (TFC)] and antioxidant activity. The herbal tea processed at 40 °C showed significantly (P < 0.05) higher TPC [485.26 ± 49.43 mg gallic acid equivalent (GAE)/ 100 g], CA (202.17 ± 1.00 mg/kg), RA (469.99 ± 1.56 mg/kg), TFC [356.86 ± 41.81 mg catechin equivalent (CE)/ 100 g], and 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity than those at other drying temperatures. Therefore, a drying temperature of 40 °C was the optimum condition for the Orthosiphon aristatus(Blume) Miq. leaves because it retained the secondary metabolite content with strong antioxidant potential.