With the increasing and widespread use of antibiotics, a large percentage of microorganisms have developed antimicrobial resistance, causing economic loss and even death. Thus, searching new class of effective antimicrobial agents is essential to cope with the continuous emergence of multi-drug-resistance of bacteria, especially resistance to anti-staphylococcal drugs. More and more phytochemicals derived from plants have been considered as a potential source of promising antibacterial agents [
1]. Some components extracted from natural plants showed inhibitory effects against
Staphylococcus aureus (SA) at low dose. However, the underlying antimicrobial action mechanisms of most natural components are currently unknown [
2]. It is quite possible that promising natural compounds can be discovered as the new antibiotic drugs [
3].
T. asiatica, belonging to the family Rutaceae, distributes in the dry areas full of hedges and bushes [
4]. The root and bark of
T. asiatica have been used in traditional medicine to treat malaria, diarrhea, cholera and cough [
5]. Its leaves have been used to treat lung and skin diseases, and rheumatism [
6]. Moreover, the plant also possesses antimicrobial, larvicidal, antidiabetic, antioxidant, antinocieptive and anti-inflammatory activities [
7‐
9]. It has been reported that the root and duramen of
T. asiatica are mainly rich in coumarins, triterpenoids and alkaloids [
10‐
12]. In our previous research, we isolated thirteen compounds from the petroleum fraction and the ethyl acetate fraction of roots of
T. asiatica and identified them [
13,
14]. These compounds were screened out based on anti-bacterial activities. Among them, chelerythrine showed more effective and potent antibacterial activity. Chelerythrine is a kind of benzo [c] phenanthridine alkaloids with many pharmacological activities, such as anti-cancer, anti-bacterial, anti-inflammatory, insecticide, anti-fibrosis activities, etc. [
15‐
19]. In past decades, a majority of studies were focused on its anti-cancer and anti-bacterial activities. It has been suggested by a previous study that chelerythrine may possess antibacterial activities and its antibacterial action mechanisms of chelerythrine against bacterium may be related to its inhibitory effects on DNA synthesis, proteinase synthesis and membrane permeability of bacterium [
20]. However, its exact action mechanisms against bacteria are currently unclear and need be further elucidated. Therefore, in this paper, we focused on elucidating its antibacterial mechanisms by detecting the changes in cell wall and cell membrane electrical conductivity, alkaline phosphatase (AKP), extracellular proteins, electrophoresis protein bands with SEM and TEM.