Floral Volatile Compounds of Passiflora edulis Sims and Poincianella pyramidalis (Tul.) L.P. Queiroz and Their Detection by Xylocopa (Neoxylocopa) nigrocincta Smith (Hymenoptera: Apidae)

Floral volatile organic compounds (VOCs) play a key role in chemical communication between plants and pollinators. Given the limited understanding of the chemical signals involved in the interactions among Passiflora edulis Sims (Passifloraceae), Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae), and Xylocopa (Neoxylocopa) nigrocincta Smith (Hymenoptera: Apidae), this study aimed to identify the floral VOCs emitted by these plant species and evaluate their detection by the antennae of X. nigrocincta. Floral VOCs were collected using dynamic headspace sampling, adsorbed in Porapak Q, and eluted with 500 µL of hexane. The resulting extracts were analyzed by gas chromatography with flame ionization detection (GC-FID), gas chromatography–mass spectrometry (GC–MS), and gas chromatography coupled with electroantennographic detection (GC–EAD). A total of 23 compounds were identified, six of which were shared by both plant species. The chemical profiles differed markedly: P. edulis was characterized mainly by methoxylated ethers and esters, whereas P. pyramidalis showed a predominance of terpenes. 1,4-dimethoxybenzene, the major compound in P. edulis, and (E)-β-ocimene, the most abundant compound in P. pyramidalis, elicited electroantennographic responses in X. nigrocincta, demonstrating that both compounds are detected by the olfactory system of these bees. These findings reveal differences in the floral VOC profiles of the two plant species and identify compounds detected by X. nigrocincta, providing a basis for future behavioral studies to investigate the role of these volatiles in plant–pollinator interactions.