Growth Inhibitory Activity of Selected Australian Syzygium Species against Malodour Forming Bacteria

Abstract

Background: Extracts produced from S. australe and S. luehmannii fruit and leaves are potent growth inhibitors of many bacterial pathogens. They may also inhibit the growth of malodour producing bacteria and thus be useful deodorant components, although this is yet to be tested. Methods: S. australe and S. luehmannii fruit and leaf solvent extracts were investigated by disc diffusion assays against significant bacterial contributors to axillary and plantar malodour formation. Toxicity was determined using the Artemia franciscana nauplii bioassay. Results: S. australe and S. luehmannii solvent extracts were good inhibitors of B. linens and C. jeikeium growth, with zones of inhibition up to 10 mm measured. S. australe extracts were generally better inhibitors of both bacterial species compared with the S. luehmannii extracts. Ethyl acetate extracts were particularly potent, with MIC values of 300 and 857 µg/mL for the S. australe fruit and leaf extracts respectively against B. linens, and 1000 and 311 µg/mL against C. jeikeium. The S. luehmannii fruit ethyl acetate extracts were similarly potent growth inhibitors, with MIC values of 571 and 203 µg/mL against B. linens and C. jeikeium respectively. S. australe aqueous and methanolic leaf extracts were also potent inhibitors of C. jeikeium (MIC's of 285 and 306 µg/mL respectively). All other extracts had moderate or low inhibitory activity. All of the most potent ethyl acetate extracts were nontoxic in the Artemia franciscana bioassay. In contrast, the methanolic and aqueous S. australe leaf extracts, as well as the aqueous and methanolic S. luehmannii fruit extracts displayed apparent toxicity. However, these results may be fallacious and instead result from the high antioxidant content of these extracts. Conclusion: The potent growth inhibition of axillary and plantar malodour producing bacteria by the Syzygium spp. extracts indicate their potential as deodorant components.

Davidsonia pruriens F. Muell. Fruit and Leaf Extracts Lack Antibacterial and Antifungal Activity

“…16 D. pruriens was deemed to be a good candidate for antibacterial screening due to its high antioxidant capacity, 25 as other high antioxidant plants have been reported to have noteworthy antibacterial activity. [32][33][34][35][36][37][38][39][40][41][42][43][44] Phenolic phytochemicals are generally strong antioxidants that protect cell constituents against oxidative damage by scavenging of free radicals, thereby averting their deleterious effects on nucleic acids, proteins and lipids in cells. 46 Interestingly, studies into the antioxidant/prooxidant effects of extracts from various plant species have demonstrated that the ability of a plant extract to exert antioxidant activity depends on multiple factors.…”

“…have also been reported to have good anticancer 26 and antibacterial activities. [40][41][42][43] Kunzea pomifera F. Muell., Acronychia acidula F.; Muell.…”

Growth Inhibitory Activity of Acronychia acidula F. Muell. Fruit Extracts Towards Malodour-forming Bacteria

“…Toxicity was assessed using an adapted Artemia franciscana nauplii lethality assay. 25 Briefly, 400 µL of seawater containing ~43 (mean 42.7, n = 125, SD 14.7) A. franciscana nauplii were added to wells of a 48 well plate and immediately used in the bioassay. Volumes of 400 µL of the reference toxin or the diluted plant extracts were transferred to the wells and incubated at 25 ± 1°C under artificial light (1000 Lux).…”