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Novel targets of pentacyclic triterpenoids in Staphylococcus aureus: A systematic review

Chung PY

Phytomedicine, 2020 Jul 15;73:152933.
PMID: 31103429 DOI: 10.1016/j.phymed.2019.152933

BACKGROUND: Staphylococcus aureus is an important pathogen both in community-acquired and healthcare-associated infections, and has successfully evolved numerous strategies for resisting the action to practically all antibiotics. Resistance to methicillin is now widely described in the community setting (CMRSA), thus the development of new drugs or alternative therapies is urgently necessary. Plants and their secondary metabolites have been a major alternative source in providing structurally diverse bioactive compounds as potential therapeutic agents for the treatment of bacterial infections. One of the classes of natural secondary metabolites from plants with the most bioactive compounds are the triterpenoids, which comprises structurally diverse organic compounds. In nature, triterpenoids are often found as tetra- or penta-cyclic structures.
AIM: This review highlights the anti-staphylococcal activities of pentacyclic triterpenoids, particularly α-amyrin (AM), betulinic acid (BA) and betulinaldehyde (BE). These compounds are based on a 30-carbon skeleton comprising five six-membered rings (ursanes and lanostanes) or four six-membered rings and one five-membered ring (lupanes and hopanes).
METHODS: Electronic databases such as ScienceDirect, PubMed and Scopus were used to search scientific contributions until March 2018, using relevant keywords. Literature focusing on the antimicrobial and antibiofilms of effects of pentacyclic triterpenoids on S. aureus were identified and summarized.
RESULTS: Pentacyclic triterpenoids can be divided into three representative classes, namely ursane, lupane and oleananes. This class of compounds have been shown to exhibit analgesic, immunomodulatory, anti-inflammatory, anticancer, antioxidant, antifungal and antibacterial activities. In studies of the antimicrobial activities and targets of AM, BA and BE in sensitive and multidrug-resistant S. aureus, these compounds acted synergistically and have different targets from the conventional antibiotics.
CONCLUSION: The inhibitory mechanisms of S. aureus in novel targets and pathways should stimulate further researches to develop AM, BA and BE as therapeutic agents for infections caused by S. aureus. Continued efforts to identify and exploit synergistic combinations by the three compounds and peptidoglycan inhibitors, are also necessary as alternative treatment options for S. aureus infections.

Matched MeSH terms: Pentacyclic Triterpenes/pharmacology
Cardiovascular Protective Effects of Centella asiatica and Its Triterpenes: A Review

Razali NNM, Ng CT, Fong LY

Planta Med, 2019 Nov;85(16):1203-1215.
PMID: 31539918 DOI: 10.1055/a-1008-6138

Centella asiatica, a triterpene-rich medicinal herb, is traditionally used to treat various types of diseases including neurological, dermatological, and metabolic diseases. A few articles have previously reviewed a broad range of pharmacological activities of C. asiatica, but none of these reviews focuses on the use of C. asiatica in cardiovascular diseases. This review aims to summarize recent findings on protective effects of C. asiatica and its active constituents (asiatic acid, asiaticoside, madecassic acid, and madecassoside) in cardiovascular diseases. In addition, their beneficial effects on conditions associated with cardiovascular diseases were also reviewed. Articles were retrieved from electronic databases such as PubMed and Google Scholar using keywords "Centella asiatica," "asiatic acid," "asiaticoside," "madecassic acid," and "madecassoside." The articles published between 2004 and 2018 that are related to the aforementioned topics were selected. A few clinical studies published beyond this period were also included. The results showed that C. asiatica and its active compounds possess potential therapeutic effects in cardiovascular diseases and cardiovascular disease-related conditions, as evidenced by numerous in silico, in vitro, in vivo, and clinical studies. C. asiatica and its triterpenes have been reported to exhibit cardioprotective, anti-atherosclerotic, antihypertensive, antihyperlipidemic, antidiabetic, antioxidant, and anti-inflammatory activities. In conclusion, more clinical and pharmacokinetic studies are needed to support the use of C. asiatica and its triterpenes as therapeutic agents for cardiovascular diseases. Besides, elucidation of the molecular pathways modulated by C. asiatica and its active constituents will help to understand the mechanisms underlying the cardioprotective action of C. asiatica.

Matched MeSH terms: Pentacyclic Triterpenes/pharmacology; Pentacyclic Triterpenes/chemistry
Gene expression changes in the human fibroblast induced by Centella asiatica triterpenoids

Coldren CD, Hashim P, Ali JM, Oh SK, Sinskey AJ, Rha C

Planta Med, 2003 Aug;69(8):725-32.
PMID: 14531023

The molecular pathways underlying the diverse biological activity of the triterpeniod compounds isolated from the tropical medicinal plant Centella asiatica were studied with gene microarrays and real-time reverse transcription polymerase chain reaction (real-time RT-PCR) to quantify the expression of 1053 human genes in human fibroblasts. Fibroblast cells grown in culture were used as a model system to evaluate the stimulation of wound healing by titrated extract from Centella asiatica (TECA) as well as by the four principal triterpenoid components of Centella. TECA treatment effects the expression of genes involved in angiogenesis and the remodeling of extracellular matrix, as well as diverse growth factor genes. The extent of expression change of TNFAIP6, an extracellular hyaluronan binding protein, was found to be largely dose-dependent, to respond most strongly to the free acids asiatic acid and madecassic acid, and to increase in expression over 48 hours of treatment. These results show that Centella triterpenes evoke a gene-expression response consistent with their prevailing medical uses in the treatment of connective tissue disorders such as wound healing and microangiopathy. The identification of genes modulated by these compounds provides the basis for a molecular understanding of Centella's bioactivity, and opportunities for the quantitative correlation of this activity with clinical effectiveness at a molecular level.

Matched MeSH terms: Pentacyclic Triterpenes
Identification, by gene expression profiling analysis, of novel gene targets in Staphylococcus aureus treated with betulinaldehyde

Chung PY, Chung LY, Navaratnam P

Res. Microbiol., 2013 May;164(4):319-26.
PMID: 23385141 DOI: 10.1016/j.resmic.2013.01.005

Staphylococcus aureus has become a serious concern in hospitals and community due to rapid adaptation to existing antimicrobial agents. Betulinaldehyde [3β-hydroxy-20(29)-lupen-28-al (BE)] belongs to pentacyclic triterpenoids that are based on a 30-carbon skeleton comprising four six-membered rings and one five-membered ring. In a preliminary study, BE exhibited antimicrobial activity against reference strains of methicillin-resistant and methicillin-sensitive S. aureus. However, the response mechanism of S. aureus to this compound is not known. In this study, the global gene expression patterns of both the reference strains in response to sub-inhibitory concentrations of BE were analyzed using DNA microarray to identify gene targets, particularly essential targets in novel pathways, i.e. not targeted by currently used antibiotics, or novel targets in existing pathways. The transcriptome analysis revealed repression of genes in the aminoacyl-tRNA synthetase and ribosome pathways in both the reference strains. Other pathways such as cell division, two-component systems, ABC transporters, fatty acid biosynthesis and peptidoglycan biosynthesis were affected only in the reference strain of methicillin-resistant S. aureus. The findings suggest that BE regulates multiple desirable targets which could be further explored in the development of therapeutic agents for the treatment of S. aureus infections.

Matched MeSH terms: Pentacyclic Triterpenes/pharmacology*
Asiatic acid stabilizes cytoskeletal proteins and prevents TNF-α-induced disorganization of cell-cell junctions in human aortic endothelial cells

Fong LY, Ng CT, Yong YK, Hakim MN, Ahmad Z

Vascul. Pharmacol., 2019 06;117:15-26.
PMID: 30114509 DOI: 10.1016/j.vph.2018.08.005

Endothelial hyperpermeability represents an initiating step in early atherosclerosis and it often occurs as a result of endothelial barrier dysfunction. Asiatic acid, a major triterpene isolated from Centella asiatica (L.) Urban, has previously been demonstrated to protect against tumor necrosis factor (TNF)-α-induced endothelial barrier dysfunction. The present study aimed to investigate the mechanisms underlying the barrier protective effect of asiatic acid in human aortic endothelial cells (HAECs). The localization of F-actin, diphosphorylated myosin light chain (diphospho-MLC), adherens junctions (AJs) and tight junctions (TJs) was studied using immunocytochemistry techniques and confocal microscopy. Their total protein expressions were examined using western blot analysis. The endothelial permeability was assessed using In Vitro Vascular Permeability Assay kits. In addition, intracellular redistribution of the junctional proteins was evaluated using subcellular fractionation kits. We show that asiatic acid stabilized F-actin and diphospho-MLC at the cell periphery and prevented their rearrangement stimulated by TNF-α. However, asiatic acid failed to attenuate cytochalasin D-induced increased permeability. Besides, asiatic acid abrogated TNF-α-induced structural reorganization of vascular endothelial (VE)-cadherin and β-catenin by preserving their reticulum structures at cell-cell contact areas. In addition, asiatic acid also inhibited TNF-α-induced redistribution of occludin and zona occludens (ZO)-1 in different subcellular fractions. In conclusion, the barrier-stabilizing effect of asiatic acid might be associated with preservation of AJs and prevention of TJ redistribution caused by TNF-α. This study provides evidence to support the potential use of asiatic acid in the prevention of early atherosclerosis, which is initiated by endothelial barrier dysfunction.

Matched MeSH terms: Pentacyclic Triterpenes/pharmacology*