ACCUMULATION OF FERULIC ACID UNDER DROUGHT STRESS IN IN VITRO CULTURE OF GARDENIA JASMONIDE VARIEGATA

Gardenia is regarded as an ornamental and medicinal plant that includes important phenolic compounds,as well as some of anti-inflammatory flavonoids. The most prevalent hydroxyl cinnamic acid in plants is ferulic acid, which is 4-hydroxy-3-methoxy cinnamic acid. It demonstrates a wide range of biological activity that can be utilized as a substrate for the synthesis of chlorogenic acid. The current study aimed to evaluate the accumulation of ferulic acid and antioxidant capacity in response to ABA and PEG and mimic the draught stress, in the in vitro culture of Gardenia jasmonides Variegata. Different concentrations of abscisic acid (ABA) and polyethylene glycol (PEG) (MW: 4000–6000) were applied individually in the culture medium of Gardenia jasmonide Variegata callus cultures to evaluate their effects on the growth as well as the ferulic acid content and antioxidant capacity. The results showed that maximum values for growth indicators (fresh and dry weight) at the fourth week of culturing (9.524 and 0.446 g, respectively) with the addition of 5 g/l PEG (M.W. 6000). As for ferulic acid, PEG (M.W. 6000) at 7.5 g/l gave 2.708 µg/g dry weight ferulic acid in the second week, which is remarked as the highest ferulic acid content.  The highest antioxidant activity was recorded using 7.5 g/l PEG (M.W. 4000) in the fourth week, which was recorded at 2491.6–812.61 µM Trolox equivalent / 100mg sample when 2,2'-azino-bis3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant power (FRAP) were subjected, respectively. Finally, it can be concluded that using PEG in various treatments had a positive impact on the growth and accumulation of ferulic acid in Gardenia jasmonide Variegata calli cultures and subsequently increased the anti-oxidant activity as opposed to using ABA.