In Vitro Antibiotic Activity of red Shallot (Allium ascalonicum), Mulberry (Morus indica), and Marigold (Tagetes erecta) Extracts against Streptococcus pyogenes

Bacterial infection is a major global health concern. One of the critical problems is the widespread of antimicrobial-resistant bacteria from inappropriate and prolonged use of antimicrobial agents in both humans and animals. Plant extracts might afford the chance to replace antibiotic drugs and reduce the emerging of antimicrobial-resistant bacteria. This study aimed to examine the antibiotic activity of ethanolic crude extracts of some Thai medicinal plants grouping in their parts as whole onions of red shallot (Allium ascalonicum), petals of marigold (Tagetes erecta), mulberry leaves, and root barks (Morus indica) to inhibit the growth of Streptococcus pyogenes. The antibiotic activities of the crude extract of three Thai medicinal plants using absolute ethanol were trialed against Streptococcus pyogenes using the disk diffusion method. Erythromycin and Ceftriaxone discs were chosen to be positive control standards as the representative of antibiotic drugs. Each dried plant extracts was prepared to test the inhibition with a concentration at 25, 50, and 75 mg/mL stock solution. The results showed that three groups from all testing groups of Thai medicinal plant extracts had the potential of antibiotic activity against S. pyogenes. The highest antibiotic activity against S. pyogenes was detected from whole onion extract red shallot followed by the extract of the mulberry leaves and root barks of mulberry strain Nakhon Ratchasima 60 (Nak 60) while the extract of marigold petal did not present antibiotic activity. The results revealed that crude extract of those two Thai medicinal plants, including red shallot and mulberry, had antibiotic activity against bacterial growth of S. pyogenes in the experiment and these medical Thai plants had potential benefits for developing as alternative treatment agents for S. pyogenes infections in both humans and animals in the future.