Dental caries represents a predominant cause of global morbidity. Estimates suggest that ~100 million microorganisms reside in the oral compartment of human mouth forming part of the normal microbiota. The buccal cavity represents a complex habitat, with bacteria capable of colonizing the hard surfaces of teeth and the soft tissue of the oral mucosa (Deo and Deshmukh, 2019). Amongst the intricate oral microbiota, Streptococcus mutans (S. mutans) is recognized as a major pathogen, forming complex biofilms that accumulate on the tooth surface contributing to the development of dental caries (Lemos et al., 2019). S. mutans not only causes dental caries, but could also result in lethal conditions such as infective endocarditis and ulcerative colitis (Nomura et al., 2020, Kojima et al., 2012). S. mutans forms biofilm on tooth surfaces and soft tissues, utilizing dietary carbohydrates like sucrose and glucans, producing organic acids that results in the demineralization of tooth enamel. Additionally, S. mutans generate robust biofilms tightly adhered and enmeshed in an extracellular matrix called exopolysaccharide (EPS) (Klein et al., 2015). EPS is a major virulence trait that provides a supportive framework for dissemination within the oral biofilm architecture. S. mutans can produce three types of glucosyltransferases (Gtfs) viz., GtfB, GtfC and GtfD that can effectively utilize dietary sucrose for the rapid synthesis of EPS (Ooshima et al., 2001). GtfB catalyzes the synthesis of water-insoluble 1,3-linked glucan, which binds the bacterium for attachment to the tooth surface. Similarly, GtfC synthesizes both water-soluble 1,6-linked glucan and water insoluble 1,3-linked glucan while GtfD synthesizes water-soluble 1,6-linked glucan, potentially providing a source of metabolizable carbohydrate for plaque formation by oral bacteria under nutrients-deficient conditions (Aoki et al., 1986).

The production of various virulence factors and the formation of biofilm by S. mutans is mainly controlled by the quorum sensing (QS) system. QS is a phenomenon in which bacteria communicate with each other by producing, detecting, releasing and responding to small oligopeptides molecules called autoinducers (AIs). These AIs molecules accumulate in a cell density-dependent manner. On reaching the threshold concentration, AI molecules activate and coordinate bacterial behavior in a cell-density-dependent manner.

S. mutans employs a QS system that depends on a small linear competence stimulating peptide (CSP) pheromone, mainly sensed via a two-competent signal system (ComDE). The comC gene encodes the ComC propeptide containing a conserved Gly-Gly motif. This propeptide is processed by the specific ABC transporter complex, ComAB, leading to synthesis of 21-CSP. This 21-amino acid polypeptide is further cleaved into an 18-aminoacide polypeptide by the extracellular SepM membrane–bound protease. The CSP pheromones accumulate in the environment, and on reaching a specific threshold concentration level, it can directly interact with the membrane-bound histidine kinase receptor. Activated ComE then results in the expression of various virulence genes encoding bacteriocins and bacteriocin-like peptides, involved in the development of competence. CSP pheromones are mainly used to regulate the expression of diversity of physiological functions such as biofilm formation, bacteriocin production, genetic transformation and production of virulence factors. Further, CSP pheromone regulates adverse environmental factors viz., oxidative stress, acidic pH, heat shock, amino acid starvation and antibiotic treatment.

Biofilm architecture mainly acts as a barrier, preventing the entry of antibiotics and increasing resistance to different antimicrobial agents. In a health care setting, virulence factors and biofilm formation results in the emergence of resistant bacteria, limiting the ability to combat dental caries (Huang et al., 2011). Currently, there are a limited number of interventions that are unable to completely eradicate cariogenesis. Chlorhexidine is a broad spectrum antimicrobial agent mainly used to prevent oral infections (Brookes et al., 2020). However, this classical mouthwash agent may alter oral physiological functions causing dysgeusia. To circumvent these challenges, increased attention is being given to plant-based quorum sensing inhibitors (QSIs) for potential use as therapeutic agents. QSIs are naturally derived from the medicinal plants (Bouyahya et al., 2017), marine microbes marine algae (Chen et al., 2019), and synthetic analogs (Paul et al., 2018). There have been a myriad ways to inhibit QS molecules and QS-controlled virulence traits (Kalia, 2013).

Medicinal plants contain phytoconstituents that can be employed for therapeutics. Plants are used in traditional medicine preparations worldwide due to their reliability, safety and efficacy (Sofowora et al., 2013). Plant-based QS inhibitors such as Carum copticum, Phlomis bruguieri, Marrubium parviflorum (Mehdipour et al., 2022), Bergenia crassifolia (Liu et al., 2017), and Mediterranean herbs (Hickl et al., 2018), have potentially inhibited QS-controlled virulence traits and biofilm of S. mutans. Similarly, essential oil derived from Curcuma longa and eucalyptus oil inhibited S. mutans biofilms at the lowest concentration of 0.5 mg/mL (Lee et al., 2011, Balhaddad and AlSheikh, 2023). Similarly, quercetin, kaempferol and embelin have inhibited QS controlled virulence factors and biofilm in S. mutans (Zeng et al., 2019a, Zeng et al., 2019b, Kole et al., 2005). The phenolic phytocompound used herein viz., 4-hydroxy-3-methoxybenzaldehyde (4-H-3-MB), is naturally derived from vanilla pods (Olatunde et al., (2022)) 4-H-3-MB has several applications in the pharmaceutical (Arya et al., 2021), food (Martau et al., 2021), and the cosmetics and perfumes industries (Olatunde et al., (2022)). In addition, 4-H-3-MB has been shown to possess anticancer, antioxidant, antimicrobial, anti-inflammatory, cardio-productive activities (Olatunde et al., (2022)). Therefore, we aimed to evaluate the QS-controlled virulence traits and antibiofilm efficacy of 4-H-3-MB against S. mutans.