2 regarding the medicinal plants within the Caatinga area, and some publications describe the rich ﬂora of this region as having many medicinal purposes [4]. This work aims at the evaluation of a preclinical assay of medicinal plants from the folk medicine of the semiarid region of the northeast against oral pathogenic microorgan- isms, in order to bioprospect a new product. 2. Materials and Methods 2.1. Plant Materials. The medicinal plants were collected from the semiarid region in the State of Para´ıba. Voucher specimen were prepared and identiﬁed at the Professor Jayme Coelho de Morais Herbarium (PRU), Federal University of Paraiba and at the Da´rdamo de Andrade Lima herbarium Agronomic Institute of Pernambuco (Table 1). 2.2. Extracts Preparation. The plant material was air dried at 40◦C and ground to a ﬁne powder. The powdered material (200 g) was extracted with 1000 mL ethanol/distilled water with 10, 20, 30, 50, and 70% (v/v) for 5 days with occasional stirring, accordingly named as HEx1, HEx2, HEx3, HEx4, and HEx5, respectively, and stored at room temperature in amber ﬂasks. 2.3. Antibioﬁlm Activity. The microorganisms used in this study included Pseudomonas aeruginosa (ATCC 27853), Streptococcus mutans (ATCC 25175), Streptococcus salivarius (ATCC 7073), Streptococcus oralis (ATCC 10557), Lactobacil- lus casei (ATCC 7469), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923), Candida albicans (ATCC 18804), Candida tropicalis (ATCC 13803), Candida krusei (ATCC 34135). Bacteria were grown in the Mueller Hinton agar medium with 5% blood agar under anaerobic conditions in anaerobic jar, at 37◦C for 48 h. Sabouraud Dextrose Agar medium was used for culturing Candidas at 25◦C for 24 h under aerobic conditions. 2.3.1. Cylinder-Plate Assay. The microorganisms were indi- vidually inoculated into tubes containing 5 mL sterile 0.9% saline solution. The suspension was adjusted spectrophoto- metrically at 625 nm which is equivalent to 106 CFU/mL. The agar was composed of 2 separate layers, and only the upper layer was inoculated. The Mueller Hinton agar (20 mL) was poured into microbiological Petri dish (100 mm × 20 mm) for the base layer. After solidiﬁcation, the other layer containing 5 mL inoculated medium, with the diﬀerent microorganisms, was distributed to the surface of each base layer. For the 5 × 1 design, six stainless-steel cylinders of uniform size (8 mm × 6 mm × 10 mm) were placed on the surface of inoculated agar, and an exactly measured volume (100 µL) of the corresponding extract was deposited into ﬁve cylinders, while the other one was ﬁlled with either the standard solution. In the bioassay, ten plates were prepared. All plates were left for 2 hour at room temperature and then incubated at 37◦C ± 1◦C (for bacteria) for 24 h and 30◦C ± 1◦C (for yeast) for 24 h. The diameter (in mm) of growth Evidence-Based Complementary and Alternative Medicine inhibition zones was carefully measured using a caliper with at least 0.1 mm accuracy. 2.3.2. Minimal Inhibitory Concentration (MIC) Determina- tion. The assay was performed by the broth microdilution method. It was performed in 96 well microplates according to the Clinical and Laboratory Standards Institute [27] procedures. The inoculums were standardized in tubes con- taining 5 mL sterile 0.9% saline solution. The suspension was adjusted spectrophotometrically at 625 nm which is equivalent to 106 CFU/mL. One hundred microlitres of each hydroalcoholic extract were serially diluted threefold with sterile Mueller Hinton broth or with sterile Sabouraud Dextrose broth in a 96-well microlitre plate for each microor- ganisms strains studied. A similar threefold serial dilution of chlorhexidine was used as a positive control against each bacterium and nystatin against each Candida. One hundred microlitres of each microorganism culture were added to each well. Ethanol/water was included as negative controls. The plate incubated at 37◦C ± 1◦C (for bacteria) for 24 h and 30◦C ± 1◦C (for yeast) for 24 h. Bacterial growth was indicated by adding 20 µL of aqueous solution of resazurin (Sigma-Aldrich) to 0.01% with further incubation at 37◦C ± 1◦C for 2 h. Viable bacteria reduced the yellow dye to a pink color. The MIC was deﬁned as the lowest concentration that inhibited the colour change of resazurin. 2.4. Bioassay with Artemia salina. This bioassay was per- formed with extracts that showed antibioﬁlm activity to evaluate the EtOH extract toxicity; it used the brine shrimp (Artemia salina) lethality test. The 50 g of eggs of A. salina were incubated in sea water (pH 8 ± 0,5 and 28◦C) at artiﬁcial light during 24–36 hours for cysts occlusion and larvae obtaining. After hatching, they were collected and put into tubes containing diﬀerent EtOH extract concentrations (2000, 1500, 1000, 500, and 250 µg/mL), and the blank control was always conduced. The set was incubated at artiﬁcial light for 24 h, and then the survivor larvae were counted to determine the LC50 using the Probit method. The bioassay was repeated three times. As the measure of extract toxicity, the LC50 value lower than 1000 µg/mL is considered bioactive [28]. 2.5. Statistical Analysis. The results were expressed as mean. Diﬀerences among means were statistically compared using the Student’s t-test for antibioﬁlm assay. The values were considered signiﬁcantly diﬀerent when P < 0.05. The software used was the Origin software. The LC50 for Bioassay with A. salina was determined according to the Probit statistical method using the software STATPLUS 2005. 3. Results and Discussion 3.1. Antibioﬁlm Activity. The selection of plant material for this study was based on the ethnobotanical data on the traditional use of plants from the semiarid region. The thirty extracts were subjected to the determination of antibioﬁlm activity against gram-positive, gram-negative