Effects of elicitors on in vitro cultures of Sauropus androgynous (sweet shoot) for sustainable metabolite production and antioxidant capacity improvement

• Published in: Acta horticulturae no. 1083; pp. 145 - 155
• Main Authors: Wee, S. L, Yap, W. S. P, Alderson, P. G, Khoo, T. J
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01.05.2015
• Subjects: antioxidant activity; antioxidants; callus culture; elicitors; free radicals; kaempferol; leaf extracts; leaves; medicinal properties; methyl jasmonate; naringin; neutralization; nutritive value; papaverine; quercetin; salicylic acid; Sauropus; secondary metabolites; shrubs; somatic embryos; tissues; South East Asia
• DOI: 10.17660/ActaHortic.2015.1083.16
• ISSN: 0567-7572

Sauropus androgynus (sweet shoot) is an underutilized shrub widely distributed in Southeast Asia, with promising medicinal properties and nutritive values. Secondary metabolites such as phenolics and flavonoids can be extracted from the leaves of sweet shoot, which serve as an antioxidant in neutralizing the damaging effects of free radicals. The leaf extract of field-grown sweet shoot failed to accumulate significant amount of antioxidant substances in nature, with only 91.86 and 241.92 µg/g FW in total phenolic and flavonoid content, respectively; and it also showed very low antioxidant activity in DPPH (54.03%) and FRAP (596.34 µg/g FW) assay. The elicitation of cultured tissues is therefore necessary to enhance the production of metabolites and to increase the antioxidant capacity in sweet shoot. In this study, the yield of antioxidant compounds was strongly influenced by both increased elicitor concentration and duration of elicitor contact. Light-induced callus cultures treated with 200 µM methyl jasmonate (MJ) gave rise to the highest total phenolic and flavonoid contents, which was 2.10-fold (192.91 µg/g FW) and 1.53-fold (370.44 µg/g FW) greater than field-grown plants after three weeks of inoculation. MJ (50, 100 µM) elicitation of light-induced callus cultures after one week had the highest antioxidant activity (DPPH, FRAP) at 1.31-fold (70.95%) and 1.19-fold (708.82 µg/g FW), respectively. Salicylic acid (SA) elicited somatic embryos showed significantly higher production in naringin (92.8-fold increment, 11471.76 µg/g FW), TBHQ (16.3-fold increment, 11625.10 µg/g FW) and kaempferol (10.7-fold increment, 2225.92 µg/g FW). Meanwhile, MJ treatment (50 µM) of somatic embryos produced increase in papaverine (8.31-fold increment, 5.57 µg/g FW) and quercetin (40.0-fold increment, 3.01 µg/g FW), after two weeks of elicitation. These results indicated that the antioxidant levels in cultured tissues of sweet shoot can be upregulated using MJ and SA as elicitors.