Antimicrobial potential of some plant extracts against Candida species

The increase in the resistance to antimicrobial drugs in use has attracted the attention of the scientific community, and medicinal plants have been extensively studied as alternative agents for the prevention of infections. The Candida genus yeast can become an opportunistic pathogen causing disease in immunosuppressive hosts. The purpose of this study was to evaluate dichloromethane and methanol extracts from Mentha piperita, Rosmarinus officinalis, Arrabidaea chica, Tabebuia avellanedae, Punica granatum and Syzygium cumini against Candida species through the analysis of Minimum Inhibitory Concentration (MIC). Results presented activity of these extracts against Candida species, especially the methanol extract.


Introduction
Medicinal plants and corresponding preparations have been used for a wide range of purposes and for many centuries people have been trying to treat diseases as well as alleviate symptoms by using different plant extracts and formulations (Cowan, 1999).Plants such as Mentha piperita (Iscan et al., 2002), Rosmarinus officinalis (Nascimento et al., 2000), Arrabidaea chica (Taylor, 1998), Tabebuia avellanedae (Machado et al., 2003), Punica granatum (Nascimento et al., 2000;Duraipandiyan et al., 2006) and Syzygium cumini (Chandrasekaram and Venkatesalu, 2004) have been used due to their antimicrobial properties.
In the 2000-2006 period, approximately 50% of new chemical molecules extracted from natural products demonstrated their importance for the development of drugs filtered thereafter.The vegetal residue was reextracted with methanol (Labsynth PA).Solvents were evaporated under reduced pressure and dried using a rotary evaporator (Buchi ® R-200 model).Crude extracts were monitored by chromatography in Thin Layer in silicagel chromatoplaques (60 F254 Merck 1.05554).The dried plant extracts were dissolved in Tween20 (Labsynth) and sterile distilled water, filtered through a 0.22-µm membrane filter (TPP) and stored at 4 °C until further use.The extracts were diluted at the moment of use with the concentration ranging from 1 to 0.001 mg/mL.
Microorganisms: Screening for antimicrobial activities: Preparation of inoculum for susceptibility tests was carried out by microdilution as set forth by the CLSI's M27-A2 recommendation protocol (CLSI, 2002).The yeasts were grown overnight at 37 °C in Sabouraud Dextrose Agar (Merck) plates, and inocula for the assays were prepared by diluting scrape cell mass in 0.85% NaCl solution, adjusted to 0.5 Mc Farland scale and confirmed by spectrophotometric reading at 625 nm.Cell suspensions were finally diluted to 5.0 × 10 3 CFU/mL.50 µL of diluted extract were added in 50 µL of RPMI-1640 in microplates (96 wells) + 100 µL of microorganisms.After that, the samples were incubated at 37 °C for 24-48 hours, in duplicate.Fluconazol was used as control standard in concentrations ranging from 64-0.125 µg/mL.The microplates were incubated at 37 °C for 48 hours.

Results
All Candida species in the in vitro test presented sensitivity to the plant extracts in use, though not for all extracts (Table 1).mainly HIV-positive patients (Erköse and Erturan, 2007).A particular characteristic of Candida is its ability to invade oral mucosa tissues by the development of hyphae, which adhere to tissue surfaces and lead to inflammation (Ellepola and Samaranayake, 2001).
Although the colonisation by Candida albicans is common and causes severe injuries in immunocompromised patients, other Candida species have been isolated from such patients, healthy patients and children with Down's syndrome, such as C. glabrata, C. krusei, C. tropicalis, C. lusitaniae, C. parapsilosis, C. guilliermondii (Erköse and Erturan, 2007;Höfling et al., 2001;Ribeiro et al., 2006;Rodrigues et al., 2004) and C. dubliniensis.These yeasts were recognised as the source of mucosal infection in HIV-positive patients and regarded as a significant cause of infections in humans, such as abdominal infections and fungemia (Erköse and Erturan, 2007).
The purpose of this study was to evaluate the potential activity of extracts from six selected plants against ten Candida species.Preparation of extracts: Each selected plant (5 g) was extracted with 600 mL of dichloromethane (Labsynth PA) with a Dispersive Extratur (Quimis ® Q-252-28 model) and

Discussion
Because of the increasing development of drug resistance to human pathogens and the appearance of undesirable effects of certain antifungal agents, the search for new antimicrobial agents is of great concern today (Phongpaichit et al., 2005).A multidisciplinary approach to drug discovery, involving the generation of truly novel molecular diversity from natural product sources combined with total and combinatorial synthetic methodologies, and including the manipulation of biosynthetic pathways, provides the best solution to the current productivity crisis facing the scientific community engaged in drug discovery and development (Newman and Cragg, 2007).
Our results revealed a strong activity of Punica granatum, Syzygium cumini and Rosmarinus officinalis (dichloromethane and methanol extracts), Arrabidaea chica (dichloromethane extract), Mentha piperita and Tabebuia avellanedae (methanol extract), with MIC varying from 0.06 to 0.001 mg/mL; and no or less activity of Arrabidaea chica (methanol extract), Mentha piperita and Tabebuia avellanedae (dichloromethane extract).The methanol extract of A. chica showed activity against yeasts within 24 hours (data not shown).However, these yeasts showed resistance to this extract after 48 hours.Among the 10 yeasts used in this study, the most resistant were C. glabrata and C. utilis, and C. krusei and C. guilliermondii were the most sensitive strains to the tested extracts.
Data obtained from other studies demonstrated positive results for these plants as well.Duraipandiyan et al. (2006) observed inhibitory effects of P. granatum, while Nascimento et al. (2000) showed activity of extracts of P. granatum, S. cumini and R. officinalis against Candida albicans.Chandrasekaram and Venkatesalu (2004) reported effectiveness of methanol extract of S. cumini and Portillo et al. (2001) found positive results for the dichloromethane extract of T. avellanedae against yeast C. albicans, thus validating our results.On the other hand, Duarte et al. (2005) obtained moderate activity testing M. piperita oil against C. albicans while Duraipandiyan et al. (2006), Portillo et al. (2001) and Dulger and Gonuz (2004) observed resistance of the extracts of S. cumini, T. avellanedae (methanol extract) and R. officinalis (ethanolic extract), respectively.Although these results are not in accordance with ours, there may be many other contributing factors, such as the seasonal period when plants are collected.
The findings presented in this paper indicate that the extracts obtained from the selected plants had anti-Candida Selected plants: the species Mentha piperita L. (leaves, voucher no.UEC 1253), Arrabidaea chica (Bonpl.)B. Verl.(leaves, voucher no.UEC 1254), Rosmarinus officinalis L. (leaves, voucher no.UEC 1264), Syzygium cumini L.(seeds, voucher no.UEC 143724), Punica granatum L. (fruit, voucher no.UEC 143723) and Tabebuia avellanedae Lor.ex Griseb (bark, voucher no.UEC 1256) were collected from the experimental field of the Research Centre for Chemistry, Biology and Agriculture, State University of Campinas (CPQBA/UNICAMP), Brazil.Voucher specimens were deposited at the Herbarium of the State University of Campinas (UEC) and were identified by Professor Jorge Yoshio Tamashiro, Ph.D.

Table 1 .
In vitro antifungal activity of dichloromethane and methanol extracts (mg/mL).Punica granatum and Syzygium cumini extracts exerted strong antifungal activity and can be a source for the development of new therapeutic agents, as they inhibited the growth of Candida.Subsequently, bioguided fractionation shall be conducted on Puninca granatum to identify the active compounds against Candida genus species.