Abstract
Oroxylum indicum, which is called Pheka in Thai, is a traditional Thai plant in the Bignoniaceae family with various ethnomedical uses such as as an astringent, an anti-inflammatory agent, an anti-bronchitic agent, an anti-helminthic agent and an anti-microbial agent. The young fruits of this plant have also been consumed as vegetables. However, there has been no report concerning its antibacterial activities, especially activities related to clinically isolated pathogenic bacteria and the in vitro antioxidant effects of this plant. Therefore, the extracts from O. indicum fruits and seeds collected from different provinces in Thailand were prepared by decoction and maceration with ethanol and determined for their in vitro antibacterial effects on two clinically isolated bacteria, Streptococcus suis and Staphylococcus intermedius, using disc diffusion assay. Ethanol extracts from O. indicum fruits collected from Nakorn Pathom province at the concentration of 1000 mg/mL exhibited intermediate antibacterial activity against S. intermedius with an inhibition zone of 15.11 mm. Moreover, it promoted moderate inhibitory effects on S. suis with an inhibition zone of 14.39 mm. The extracts prepared by maceration with ethanol promoted higher antibacterial activities than those prepared with water. The ethanol extract from the seeds of this plant, purchased in Bangkok, showed stronger in vitro antioxidant activities than the other extracts, with an EC50 value of 26.33 µg/mL. Phytochemical analysis suggested that the seed ethanol extract contained the highest total phenolic and flavonoid contents (10.66 g% gallic acid equivalent and 7.16 g% quercetin equivalent, respectively) by a significant amount. Thin layer chromatographic analysis of the extracts showed the chromatographic band that could correspond to a flavonoid baicalein. From the results, extracts from O. indicum fruits have an in vitro antioxidant effect, with antibacterial potential, on clinically pathologic bacteria and they contain an antioxidant flavonoid which could be developed for medicinal and pharmaceutical purposes in the future.
Highlights
Ethnoveterinary medicine (EVM) is the traditional practice of using natural products, mainly plant extracts, to protect, treat or support animal health [1]
The extracts from O. indicum fruits and seeds collected from different provinces in Thailand were prepared by decoction and maceration with ethanol and tested for in vitro antibacterial effects on two clinically isolated bacteria, namely Streptococcus suis and Staphylococcus intermedius, by disc diffusion assay, and they were tested for in vitro antioxidant effects using the DPPH scavenging method
The dose effectiveness was compared between water and ethanol extracts, with the water extracts exhibiting less effectiveness than the ethanol extracts ranging from two-fold to 64-fold (100 to 250 mg/mL fruit extracts for Staphylococcus intermedius, 6.25 to 25 mg/mL seed extracts for Staphylococcus intermedius, 250 to 500 mg/mL fruit extracts for Streptococcus suis, and 1.5625 to 100 mg/mL seed extracts for Streptococcus suis)
Summary
Ethnoveterinary medicine (EVM) is the traditional practice of using natural products, mainly plant extracts, to protect, treat or support animal health [1]. Natural products are sources of new chemical diversities and pharmaceutical components. They are future antimicrobial candidates, which could provide more effective and less toxic antimicrobial compounds [2]. The seeds have been used as purgative while the seed paste is applied to the throat for quick relief of tonsil pain [4,5]. Many flavonoids such as baicalein and biochanin A were previously reported in the pods, seeds and root bark of this plant [6,7,8,9,10,11]
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