Investigation of Chemical Constituents in Acacia saligna (Labill.) H.L.Wendl. Related to Antidiabetic Activity
- Publication Type:
- Thesis
- Issue Date:
- 2023
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Acacia saligna is native to Western Australia that can grow in extreme conditions. This plant produces secondary metabolites, including diverse flavonoids, cinnamic acids, and benzoic acid derivatives, to support its defence system. Reports have revealed that extracts and phytochemicals of Middle Eastern and African species possess varied bioactivities, such as antioxidant, antibacterial, antifungal, antiinflammation, and antidiabetic properties. However, there has not yet been researched on Australian species. Therefore, this study aimed to investigate the antidiabetic compounds from Australian A. saligna by bioassay-guided fractionation using a combination of rapid in vitro assays and 3T3-L1 adipocyte-based assays.
This study discovered that the methanolic extract of flowers (FL-MeOH), methanolic extract of leaves (LF-MeOH), and methanolic extract of bark (BK-MeOH) have excellent properties as antioxidants, α-glucosidase inhibitors, inhibitors of cellular reactive oxygen species (ROS), and modulators of glucose uptake. Additionally, our mitochondrial study revealed that these extracts can restore adipocytes’ mitochondria by reducing mitochondrial ROS (mt-ROS) and increasing mitochondrial membrane potential (MMP). Further fractionation of the methanolic extracts using column chromatography afforded various phytochemicals. There are five compounds isolated from FL-MeOH: naringenin; naringenin-7-O-α-L-arabinofuranoside; isosalipurposide; quercitrin 4; and D-(+)-pinitol 79a. Six compounds were isolated from LF-MeOH: (−)-epicatechin, quercitrin; myricitrin; 2,4-di-t-butylphenol; (−)-pinitol; and (3S*,5S*)-3-hydroxy-5-(2-aminoethyl) dihydrofuran-2(3H)-one. Isolated phytochemicals BK-MeOH were (−)-epicatechin, D-(+)-pinitol, and sucrose. Furthermore, the bioassay outcomes indicated that (−)-epicatechin performed best in reducing cellular ROS and mt-ROS, aligning with its inhibitory activities against DPPH and ABTS radicals. Marked increases in cellular glucose uptake and MMP values were observed from treatment with naringenin, naringenin-7-O-α-L-arabinofuranoside, D-(+)-pinitol, and (–)-epicatechin reflecting the positive effect of their respective extracts in glucose uptake.
To gain more insight into possible mechanisms, further investigation was carried out using immunoblot and quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Our findings revealed that FL-MeOH exerted marked increases in glucose uptake and phosphorylated 5' adenosine monophosphate-activated protein kinase-α (p-AMPK-α) due to the presence of isosalipurposide, quercitrin, naringenin, and naringenin-7-O-α-L-arabinofuranoside. On the other hand, LF-MeOH showed corresponding effects due to quercitrin, myricitrin, and (−)-epicatechin. FL-MeOH and its chemical constituents, naringenin and D-(+)-pinitol, consistently increased MMP values, p-AMPK-α levels, and transcriptional levels of key regulators and reduced transcriptional levels of proinflammatory markers. Overall, the extracts and isolated chemical constituents of A. saligna demonstrated antidiabetic activities on 3T3-L1 adipocytes by reducing ROS and mt-ROS, stimulating glucose uptake, and modulating transcriptional levels of adiponectin, PGC-1α, and mtTFA while also reducing pro-inflammatory TNF-α and IL-6 mRNA levels to promote mitochondrial biogenesis.
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