Diterpenoids are composed of 4 isoprene units and are derived from geranyl pyrophosphate. These compounds are widely found in the plant kingdom, insects, fungi, and marine organisms and have antiviral, antitumor, anti-inflammatory, and antibacterial effects. Natural diterpenoids have the advantages of low toxicity, broad antibacterial spectrum and low drug resistance, and the combination with antibiotics can enhance the antibacterial effect.
Diterpenoids include acyclic diterpenes, monocyclic diterpenes, bicyclic diterpenes, tricyclic diterpenes, tetracyclic diterpenes and so on. Bicyclic diterpenes can be subdivided into hemiphilic alkane type, crotane type, sea hare alkane type, slender tooth alkane type alkane, viscidane alkane type, etc.
Diterpene compounds mainly inhibit growth leading to bacterial death by disrupting cell walls and cell membranes, affecting their metabolic pathways, or binding to proteins on the cell surface and preventing nutrient uptake.
1. Staphylococcus aureus
The antimicrobial activity of four compounds isolated from S. aureus was determined. The methicillin-resistant Staphylococcus aureus (MRSA) was inhibited by the glycosylation of the hydroxyl group on the backbone of the diterpene sincoetsin C. The anti- MRSA activity was enhanced by the methoxylation at the C-7 and C-16 positions, and the activity was also affected by the substituent at the C-13 position. The substituent at C-13 also had an effect on the activity.
2. Streptococcus mutans
The inhibition of the growth of caries-causing bacteria Streptococcus mutans in vitro was observed by the growth, acidification and biofilm formation of Streptococcus mutans, and it was found that rosin acid inhibited the ATP activity by about 80%, and rosin acid could inhibit the biofilm formation of Streptococcus mutans.
3. Candida albicans
(E)-labda-8 (17), 12-diene-15, 16-dial was isolated from black fruit ginger, which had an inhibitory effect on Candida albicans, causing cell lysis and retarding the growth of Candida albicans by inhibiting the uptake of substrates in a concentration-dependent manner. It also binds to certain transporter proteins on the surface of fungal cells, preventing their nutrient uptake and thus inhibiting their growth.
4. Staphylococcus epidermidis
Rosolic acid has antibacterial activity against Staphylococcus epidermidis, but it is poorly selective for bacterial cells and causes cell membrane damage by inducing intracellular lactate dehydrogenase leakage at high concentrations.
The aqueous decoction and alcoholic extract of C. cepacia showed significant anti-inflammatory effects on xylene-induced swelling of mouse earwalls, and significantly inhibited the delayed hypersensitivity reaction in mice caused by 2,4-dinitrofluorobenzene, and had a significant inhibitory effect on the proliferation of T and B lymphocytes in a dose-dependent manner, i.e., it had an inhibitory effect on cellular immunity.
The anti-tumor mechanism of diterpenoids mainly includes:
1. Induction of apoptosis of tumor cells.
The antagonistic effects of many diterpenoids of plant origin on tumors are closely related to the induction of apoptosis, but the specific apoptotic pathways induced are not the same.
2. Diterpenoids inhibit the abnormal proliferative effect of tumor cells.
3. Direct cytotoxic effects.
4. Inhibition of tumor angiogenesis.
5. Reduction of mitochondrial membrane potential in tumor cells.
6. Alteration of free calcium ion concentration in tumor cells.