Abstract
A series of nitrogen-containing apigenin analogs 4a–j was synthesized via Mannich reactions to develop anticancer, antibacterial, and antioxidant agents from plant-derived flavonoids. The chemical structures of these compounds were confirmed using 1H-NMR, 13C-NMR, and ESI-MS. The in vitro biological activities of the analogs were evaluated via assays of their antiproliferative, antibacterial, and antioxidant activities. The prepared apigenin analogs exhibited different antiproliferative activities against four human cancer cell lines, namely human cervical (HeLa), human hepatocellular liver (HepG2), human lung (A549), and human breast (MCF-7) cancer cells. Compound 4i showed the most favorable in vitro antiproliferative activity with IC50 values of 40, 40, 223, and 166 μg/mL against HeLa, HepG2, A549, and MCF-7, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity assay also showed that 4i had the most potent antioxidant activity, with the smallest IC50 value (334.8 μg/mL). The antibacterial activities of the analogs were determined using a two-fold serial dilution technique against four pathogenic bacteria, namely Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. All the prepared apigenin analogs exhibited more potent activities than the parent apigenin. Compounds 4h and 4j, in particular, exhibited the best inhibitory activities against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis with MIC values of 3.91 and 1.95 μg/mL, respectively.
Highlights
Flavonoids are important components of various traditional Chinese medicines and phytomedicines that bear C6-C3-C6 skeletons [1,2]
We have synthesized a series of 8-aminomethylated apigenin analogs
Bioactivity assays showed that all the synthesized compounds exhibited greater potential antiproliferative, antibacterial, and antioxidant activities compared with the parent apigenin
Summary
Flavonoids are important components of various traditional Chinese medicines and phytomedicines that bear C6-C3-C6 skeletons [1,2] In addition to their physiological roles in plants, these compounds exhibit anticancer, antioxidant, anti-aging, and antibacterial activities [3,4,5]. Flavonoids display antibacterial activity by inhibiting nucleic acid synthesis [6,7,8], cytoplasmic membrane function [9,10,11], and energy metabolism [12]. They are generally classified as flavones, flavonols, flavanones, flavanonol, or isoflavones, based on the degree of oxidation of the carbon-3 bond (C-3) and the connection position of the B-ring [13]. Over 4,000 flavonoids have been identified, and several of these compounds showed diverse pharmacological activities, such as antimicrobial [15], antiallergic [16], antidiabetic [17], anti-inflammatory [18], antiviral [19], antimutagenic [20], antithrombotic [21], antioxidant [22], anticarcinogenic [23], and hepatoprotective [24] effects
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