Changes in secondary metabolite contents of Arnica chamissonis Less. in response to different harvest time, flower developmental stages and drying methods

The relative values of secondary metabolites may be impacted by harvesting time and post-harvest drying methods.

The effects of various harvesting stages of flower and drying methods were investigated on the quality and quantity of secondary metabolites of A. chamissonis Less. grown in the field.

The flowers were harvested in early May, June and July from four different developmental stages (stage 1: opening bud; stage 2: all radial florets or less than half of tubular florets opened; stage 3: all radial and tubular florets opened; stage 4: radial florets withering and seed formation). Also, the maximum collection of inflorescences during two years of trial was considered for drying method treatments (shade and sun drying, oven drying at 40 and 50 °C, and microwave drying at 500 and 1000 W power).

Results showed that the highest and the lowest total phenols were obtained in the second and first harvest date at flower maturity stages of 3 and 4, respectively. However, the highest luteolin and apigenin contents were obtained in the third harvest time at flower development stage 1. In the second experiment, the flower heads treated by shade contained the highest total phenols content followed by oven drying at 40°C. Moreover, oven drying was the most favorable method for preserving of other main secondary metabolites including total flavonoid, rutin, luteolin and apigenin.

Different harvesting dates at various flower bud phenological stages had significant effect on total phenols, flavonoids, rutin, luteolin and apigenin contents.