Flavone-Rich Fractions and Extracts from Oroxylum indicum and Their Antibacterial Activities against Clinically Isolated Zoonotic Bacteria and Free Radical Scavenging Effects

Abstract

Oroxylum indicum extracts from the seeds collected from Lampang and Pattani provinces in Thailand, and young fruits and flowers exhibited in vitro display antioxidant and antibacterial activities against clinically isolated zoonotic bacteria including Staphylococcus intermedius, Streptococcus suis, Pseudomonas aeruginosa, β-hemolytic Escherichia coli and Staphylococcus aureus. The orange crystals and yellow precipitates were obtained from the preparation processes of the seed extracts. The orange-red crystals from the seeds collected from Lampang province exhibited strong in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging effects (EC50 value = 25.99 ± 3.30 μg/mL) and antibacterial effects on S. intermedius and β-hemolytic E. coli while the yellow precipitate from the same source exhibited only antioxidant activity. Quantitative analysis of phytochemicals in O. indicum samples by spectrophotometric and HPLC techniques showed that they contained different amounts of total phenolic, total flavonoid and three major flavones; baicalin, baicalein and chrysin contents. Young fruit extract, which contained low amounts of flavone contents, still promoted antibacterial effects against the tested bacteria with IC50 values lower than 1 mg/mL and MIC values between 4 to 10 mg/mL in S. intermedius, S. aureus and S suis while higher IC50 and MIC values against P. aeruginosa and β-hemolytic E. coli were found. From scanning electron microscopy, the extract of the young fruit of O. indicum promoted morphological changes in the bacterial cells by disrupting the bacterial cell walls, inducing leakage of the cellular content, and generating the abnormal accumulation of cells. The mechanism of action of the extract for this antibacterial effect may be the disruption of the cell membrane and abnormal cell aggregations. Regression analysis of the results suggests the correlation between total phenolic and total flavonoid contents and antioxidant and antibacterial effects. Baicalin was found to have a high correlation with an inhibitory effect against β-hemolytic E. coli while three unidentified peaks, which could be flavones, showed high correlations with an inhibitory effect against S. intermedius, S. suis, P. aeruginosa and S. aureus.

The Influence of Different Extraction Techniques on the Chemical Profile and Biological Properties of Oroxylum indicum: Multifunctional Aspects for Potential Pharmaceutical Applications

“…Flavonoids mostly belong to polyphenol compounds, thus TPC should be greater than TFC theoretically. However, different reference substances were used in the determination (gallic acid for TPC and rutin for TFC), and different extraction methods may lead to incomplete or destroyed extraction of polyphenols, thus TFC of ME and ASE extracts were slightly greater than TPC [ 10 ]. The finding corroborates with research performed by Zheleva-Dimitrova et al [ 18 ], they concluded that SOXE and ASE were useful to extract phenolic and flavonoids compounds from plants.…”

“…It has been used in folk remedies for centuries with a certain medicinal value, which is mainly used to treat cough-based respiratory diseases [ 6 ]. Modern pharmacological studies have demonstrated that O. indicum has a wide spectrum of biological activities, including antioxidant [ 7 , 8 ], anti-inflammatory [ 9 ], antibacterial [ 10 ], analgesic [ 11 ], anticancer [ 12 ], and antidiabetic properties [ 13 , 14 ]. Phytochemical research indicates that flavonoids are the main chemical components of O. indicum [ 13 ].…”

Determination of Phytochemical Contents in Extracts from Different Growth Stages of Oroxylum indicum Fruits Using HPLC-DAD and QAMS Methods

“…This compound was isolated using the chromatographic techniques as mentioned in Section 3.3.2.1, then structurally identified using spectroscopic and spectrometric techniques. According to the UV spectrum, the 1 H-NMR and 13 C-NMR data and the mass spectra, it was identified as oroxylin A (7) (Figure 3A). In contrast, the HPLC chromatogram of the young fruit extracts exhibited the constituent OI2, which eluted at a retention time of 14.61 min.…”

“…The major components in the leaves were found to be baicalein, scutellarein and their glucuronide compounds [20]. From our previous work, besides three major compounds, baicalin, baicalein and chrysin, which were quantitative analyzed using the developed HPLC method [13], there were another three peaks that could be found in the extracts from O. indicum such as the seeds and fruits. These three unidentified peaks, along with any other unknown peak in O. indicum extracts, should be identified and quantitatively analyzed.…”

“…The in vitro DPPH scavenging effects, the total phenolic and total flavonoid contents and an LC-MS chromatogram of different plant parts including flowers, pedicels, Molecules 2023, 28, 6837 2 of 15 leaves, stalks, seeds and fruits, tissue-cultured plants and callus cultures of O. indicum were also reported [12]. The fruit extract at a concentration of 5 mg/mL caused morphological changes in bacteria by disrupting the bacterial cell walls, inducing the leakage of the cellular content and generating an abnormal accumulation of cells, suggesting that its underlying mode of action is the disruption of the cell membrane and abnormal cell aggregations [13]. Flavonoids were found to be major compounds in O. indicum.…”