Nutritional Value and Antimicrobial Activity of Pittosporum angustifolium (Gumby Gumby), an Australian Indigenous Plant

Abstract

The indigenous endemic plant P. angustifolium has received attention for nutraceutical and therapeutic applications in Australia. This study investigates for the first time the nutritional value (macro- and micronutrients, minerals, trace elements, polyphenols, carotenoids, saponins and antioxidant capacity) and antimicrobial activity of different botanical parts of P. angustifolium, either collected from the wild or cultivated. Different botanical tissues, geographic location and growing condition (wild vs. cultivated) showed significant (p < 0.05) effects on the tested bioactive compounds, with the leaves having significantly (p < 0.05) higher levels than the stems. Saponins and polyphenols could be identified as the main bioactive compounds in the leaves with up to 4% per dry weight. The extracts of P. angustifolium leaves and stems showed strong antioxidant and antimicrobial activities, especially against Candida albicans. These activities correlated (R² = 0.64-0.92; p < 0.05) with the levels of polyphenols and saponins, indicating their biologic potential. Findings from this study may provide information for future applications of P. angustifolium in the functional ingredient or nutraceutical industry.

Keywords: Australian indigenous plant; Gumby Gumby; antimicrobial activity; bioactive compounds; nutrients.

Figure 1

Main polyphenolic compounds identified in P. angustifolium leaves and stem.

Figure 2

Contents of vitamin C (A) and folates (B) in the studied P. angustifolium samples; Data present means ± SD (n = 3); Different letters indicate significant differences at α = 0.05; RDI for vitamin C and folates are reported at 45 mg/day and 400 µg/day for adults, respectively [34].

Figure 3

Free (A) and bound (B) phenolic compounds in the studied P. angustifolium samples; Data present means ± SD (n = 3); Different letters of individual phenolic compounds indicate significant differences at α = 0.05.

Figure 4

Carotenoids identified in the studied P. angustifolium samples. Data present means ± SD (n = 3); Different letters of individual carotenoid compounds indicate significant differences at α = 0.05.

Figure 5

2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity of P. angustifolium extracts. EC₅₀ value is the amount/concentration of the sample extract or ascorbic acid necessary to scavenge/reduce the initial DPPH radical concentration by 50% (50% effective concentration). Different letters within individual extract indicate significant differences at α = 0.05.