Antioxidant and Anti-Inflammatory Activities of Endemic Plants of the Australian Wet Tropics

Abstract

Plants have been a vital source of natural antioxidants since ancient times. Plants growing under various abiotic stress conditions often produce more defensive secondary metabolites such as phenolics, flavonoids, and terpenoids during adaptation to the environment. Many of these secondary metabolites are known to possess antioxidant and anti-inflammatory properties. This study tested seven plants sourced from the mountaintop areas (above 1000 m elevation) of Mount Lewis National Park (falls under the Wet Tropics of Queensland), Australia, for their antioxidant and anti-inflammatory activities. Of the seven studied plants, hydroethanolic extracts of six plants (Leptospermum wooroonooran, Ceratopetalum hylandii, Linospadix apetiolatus, Garcinia brassii, Litsea granitica, and Polyscias willmottii) showed high 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging activity in a dose-dependent (25–1000 μg/mL) manner. At the highest concentration of 1 mg/mL, the DPPH free radical scavenged percentage varied between 75.4% and 92.3%. Only the species Alyxia orophila was inactive in the DPPH free radical scavenging assay. Pseudo-IC50 values of the extracts’ ferric reducing antioxidant power (FRAP) based on dose-response curves showed a significant positive correlation with total phenolic content. Five out of the seven plants, namely G. brassii, C. hylandii, L. apetiolatus, L. wooroonooran, and A. orophila, showed inhibitory effects on the secretion of proinflammatory cytokines, tumour necrosis factor (TNF), and interleukins (IL)-23 in a lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMCs) assay. The results of this study demonstrate the value of tropical mountaintop plants in the biodiscovery of antioxidant and anti-inflammatory lead compounds.

The In Vitro Antioxidant and Anti-Inflammatory Activities of Selected Australian Seagrasses

“…Using a modified literature method [ 29 , 30 , 31 ], the DPPH radical scavenging activity of each seagrass root and aerial extract was evaluated (performed in triplicate) by combining 100 μL of root and aerial extracts (and separated root or aerial extract for Z. muelleri ) at five different concentrations (500, 250, 125, 62.5, and 32.5 μg/mL in MeOH) with 200 μL of 0.1 mM DPPH (in MeOH). Absorbances were measured using a microplate reader (SPECTROstar ® Omega, BMG Labtech, Sydney, Australia) at 517 nm after 1 h of incubation in the dark condition at room temperature.…”

Approaches, Strategies and Procedures for Identifying Anti-Inflammatory Drug Lead Molecules from Natural Products

“…Furthermore, monoterpenes, sesquiterpenes, and diterpenes were higher in young leaves than their mature leaves [ 3 , 4 ]. Recent studies conducted by Wangchuk’s group at James Cook identified the pharmaceutical potential of Australian Wet Tropics plants affected by climate change, and they have also discovered two novel drug lead molecules from one of the ecologically-directed tropical montane cloud forest plants [ 53 , 54 ]. Similarly, potent small molecules anti-inflammatory excretory-secretory products (ESP) derived from parasitic helminths were identified using metabolomics and lipidomics platforms [ 55 , 56 ].…”

Climate-Affected Australian Tropical Montane Cloud Forest Plants: Metabolomic Profiles, Isolated Phytochemicals, and Bioactivities

“…Studies have suggested that SMs, which function as plant defence mechanisms, possess intriguing pharmacological properties, including antioxidant and anti-inflammatory properties [178]. For instance, a novel galloyl-lawsoniaside A isolated from U. metrosideros leaf significantly suppressed pro-inflammatory cytokines, such as interferon-gamma and interleukins-17 (IL-17) and IL-18, and thus was identified as a new anti-inflammatory druglead molecule [132].…”

“…Osthol isolated from Leionema ellipticum also showed anti-inflammatory activity [143,146]. A study by Yeshi et al [178] analysed crude extracts from the leaves of seven plant species endemic to WTWHA of FNQ. Five of the seven plant species showed potent antioxidant and anti-inflammatory activities in in vitro human peripheral blood cells (PBMCs) assay [178].…”

“…A study by Yeshi et al [178] analysed crude extracts from the leaves of seven plant species endemic to WTWHA of FNQ. Five of the seven plant species showed potent antioxidant and anti-inflammatory activities in in vitro human peripheral blood cells (PBMCs) assay [178]. About 30 plant species growing in the WTWHA were reported as medicinal plants used for many years by indigenous communities to treat various diseases and ailments, including inflammation-related diseases [179].…”