Essential Oils from Four Brazilian Piper Species: GC-MS and HPTLC Profiling, Cytotoxicity Screening, and Behavioral...

Background: Brazilian Piper species are chemically diverse sources of volatile metabolites, yet direct comparative datasets integrating complementary analytical and biological endpoints remain limited. Methods: This study compared hydrodistilled essential oils (EOs) from Piper amalago, P. diospyrifolium, P. grazielae, and P. solmsianum using GC-MS, HPTLC fingerprinting, qualitative HPTLC-DPPH visualization, in vitro cytotoxicity screening, and behavioral assays with imported fire ants. Results: GC-MS revealed distinct chemical profiles among the four analyzed EOs. P. solmsianum was dominated by monoterpenes, mainly β-pinene (28.21%) and myrcene (24.73%); P. diospyrifolium was characterized by trans-β-caryophyllene (22.06%); and P. grazielae by germacrene D (14.06%), trans-β-caryophyllene (12.53%), and bicyclogermacrene (9.50%). P. amalago showed a mixed terpene profile containing bicyclogermacrene (11.00%), spathulenol (9.21%), and β-phellandrene (8.12%). HPTLC generated visually discriminative fingerprints that complemented the GC-MS profiles and identified chromatographic zones for subsequent compound-level characterization. Qualitative HPTLC-DPPH visualization revealed DPPH-reactive zones, most prominently in P. grazielae. The EOs produced moderate, cell-line-dependent cytotoxic responses, with P. grazielae showing the lowest IC₅₀ values against BT-549 (45 µg/mL) and SK-OV-3 (43 µg/mL) cells and modest apparent selectivity indices (1.56-1.72). P. amalago reduced sand removal by hybrid imported fire ants at 31.25 µg/g, whereas P. solmsianum reduced sand removal by hybrid and red imported fire ants at 62.5 and 31.25 µg/g, respectively; neither oil caused mortality at 125 µg/g. Conclusions: The four EOs showed distinct chemical and biological profiles under the standardized conditions employed. P. grazielae showed the lowest IC₅₀ values in the cytotoxicity screening and the most prominent DPPH-reactive chromatographic response, whereas P. amalago and P. solmsianum produced measurable nonlethal deterrence of fire ant digging behavior.