A saponin isolated from Agapanthus africanus differentially induces apoplastic peroxidase activity in wheat and displays fungicidal properties

• Published in: Acta physiologiae plantarum 2015-11, Vol.37 (11), Article 246
• Main Authors: Cawood, Maria E., Pretorius, Johan C., van der Westhuizen, Jan H., van Heerden, Fanie R.
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Life Sciences; Original Article; Plant Anatomy/Development; Plant Biochemistry; Plant Genetics and Genomics; Plant Pathology; Plant Physiology
• ISSN: 0137-5881; 1861-1664
• DOI: 10.1007/s11738-015-1992-7

A spirostane with an attached trisaccharide, (25 R )-5 α -spirostane-2 α ,3 β ,5 α -triol 3- O -( O - α - l -rhamnopyranosyl-(1 → 2)- O -( β - d -galactopyranosyl-(1 → 3))- β - d -glucopyranoside), was isolated and identified from the aerial parts of Agapanthus africanus by activity-guided fractionation. Fungicidal properties of the crude extract, semi-purified fractions as well as the purified active saponin from A. africanus were screened in vitro against Fusarium oxysporum . At a concentration of 1 mg mL −1 , the crude extract and semi-purified ethyl acetate and dichloromethane fractions showed significant antifungal activity. The purified saponin inhibited the in vitro mycelial growth of F. oxysporum completely (100 %) at a concentration of 125 µg mL −1 . Furthermore, to verify previously observed induced resistance by crude extracts of A. africanus towards leaf rust, intercellular PR-protein activity was determined in wheat seedlings following foliar application of the purified saponin at 100 µg mL −1 . In vitro peroxidase enzyme activity increased significantly (60 %) in wheat seedlings 48 h after treatment with the purified saponin, demonstrating its role as an elicitor to activate a defence reaction in wheat.