Abstract:

The aim of the present study was to evaluate the effects of four drying methods including hot air drying, shade
drying, vacuum drying and vacuum freeze drying on polyphenol compounds and antioxidant activity of Lonicera japonica
flower. The contents of total phenols and individual phenolic compounds were determined by Folin-Ciocalteu and high
performance liquid chromatography (HPLC), respectively. In addition, the free radical scavenging activities of polyphenols
extracted from Lonicera japonica flower against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and 2,2’-azinobis
(3-ethylbenzothiazoline-6-sulfonate acid) diammonium salt (ABTS) radicals were determined. The results showed that the contents
of total phenols and individual phenolic compounds were affected by four drying methods, especially by vacuum freeze drying.
The antioxidant activities of polyphenols extracted from Lonicera japonica flower were also significantly affected by four drying
methods (P < 0.05). The IC50 of vacuum freeze dried Lonicera japonica for scavenging capacity against DPPH, hydroxyl and
ABTS radicals were 5.43, 17.64 and 44.32 μg/mL, respectively. It was clearly indicated that the IC50 of hot air dried, shade dried
and vacuum dried Lonicera japonica was higher than that of vacuum freeze dried sample. Correlation analysis exhibited a high
relationship between phenolic acid and antioxidant activity (P < 0.05). Based on these results, vacuum freeze drying is the most
suitable method for retaining phenolic compounds and antioxidant activities in Lonicera japonica.

Key words: Lonicera japonica, drying methods, polyphenols, antioxidant activity