Aim:The aim of this study is to evaluate the in vitro antimicrobial activity of plant extracts and chemical fractions of Sideroxylon obtusifolium T.D. Penn on Streptococcus mutans, Streptococcus oralis, Streptococcus salivarius, Streptococcus parasanguinis, and Candida albicans as well as to identify the chemical classes found in the bioactive extracts possessing better activity. Materials and methods:Freeze-dried hydroalcoholic extracts of the bark and leaves (LC and LF respectively) and ethanol extracts of bark and leaves (EC and EF respectively) of S. obtusifolium were assessed for antimicrobial potential by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration, and minimum fungicidal concentration (MFC). The tests were performed by microdilution method (in triplicate) in three independent experiments. Phytochemical characterization was performed by quantification of total polyphenols, total flavonoids, and condensed tannins. Results:The EC extract presented weak antimicrobial potential on the growth of S. mutans (MIC = 1000 µg/mL); all extracts showed moderate inhibitory activity on the growth of C. albicans (MIC = 500 µg/mL). The dichloromethane and n-butanol fractions of LF extracts showed moderate growth inhibitory activity (MIC = 250 µg/mL) on C. albicans and fungicide potential (MFC/MIC = 2). The phytochemical characterization revealed a Conclusion:The dichloromethane and n-butanol fractions of S. obtusifolium LF extract showed antifungal activity against C. albicans, with the potential for bioprospection of phytocompounds for the treatment of periodontal fungal diseases caused by this microorganism. The effect may be related to phytochemical compounds from the polyphenol and condensed tannin classes.Clinical significance: Research for new oral microbial disease treatment alternatives in bioactive compounds from medicinal plants is of clinical relevance and scientific interest since many therapeutic antifungal agents do not obtain the effectiveness expected due to microbial resistance, or to adverse effects on human tissues.

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