Caracterização química e avaliação do efeito antibacteriano e atividade sinérgica dos óleos essenciais de pogostemon cablin,Monarda fistulosa e cuminum cyminum, e do patchoulol frente a bactérias de importância clínica

Abstract

Dental caries is a chronic multifactorial infectious disease characterised by the accumulation of microorganisms on the tooth surface, forming a cariogenic biofilm, caused mainly by the bacterium Streptococcus mutans. Another health problem of global concern is the DTA's, which are toxic-infectious diseases caused by the consumption of food or drink contaminated by chemical, hysical or biological agents, the latter being the most common, especially bacteria. DTA`s resulting from bacterial infections are mainly caused by Staphylococcus aureus, Clostridium spp., Bacillus spp., Salmonella spp., Shigella spp., Escherichia coli and Klebsiela pneumoniae. Given these scenarios, research is needed into the search for new antimicrobial agents, such as the study of medicinal plants with possible antimicrobial properties. In this sense, essential oils of plant origin and their isolated constituents are alternatives for the development of new medicines. Previous studies on patchouli essential oil and its main component, patchoulol, have reported various biological properties, including antiulcer, anti-inflammatory and antimicrobial activity. Monarda rosa is a plant of great interest and the essential oil of one of its chemotypes contains more than 90% geraniol and has antimicrobial, antitumour and anthelmintic properties. Another plant worth mentioning is cumin, whose oil contains around 30 per cent cuminaldehyde and exhibits antidiabetic, antimicrobial and antioxidant activity. Therefore, the aim of this study is to chemically characterise these oils and the major component isolated from patchulol oil, as well as to assess their effects against cariogenic bacteria and food contaminants. The components of the oils were identified and quantified using GC/MS and GC/DIC, respectively. MS and NMR spectrometric techniques were used to elucidate the structure of the predominant constituent. Antibacterial activity was determined using the microdilution in wells technique in order to find the MIC and MBC of the substances against bacteria of clinical interest. The synergistic effect of patchouli oil (OEPC) and patchoulol with antibiotics (ampicillin, benzylpenicillin and oxacillin) was assessed using the checkerboard test on a strain of S. aureus. Analysis of the oils resulted in the identification of 26 constituents, 17 of which were present in OEPC, five in monarda rosa (OEMF) and six in cumin (OECC). The major components identified in the oils were: patchoulol (37.1%), α-bulnesene (17.42%), α-guaiene (13.96%) and seichelene (8.52%) for OEPC; geraniol (92.3%) for OEMF; and cuminaldehyde(51.7%), o-cymene (21.1%) and γ-terpinene (11.7%) for OECC. The MICs for OEPC, OEMF and OECC ranged from 250 to 8000 µg/mL and for patcoulol, a constituent isolated from OEPC, from 31.25 to 62.5 µg/mL. The CBM of the oils ranged from 500 to 8000 µg/mL and of the isolate from 31.25 to 125 µg/mL. OEPC and patchoulol showed synergism when combined with oxacillin. Thus, of the three oils tested, OEPC showed the best activity, as did its main constituent, patchoulol. Further studies into the therapeutic potential of these natural products are therefore necessary.