**4. Conclusions**

In the present study, we have isolated twelve (**1**–**12**) components and identified 40 volatile compounds in Mexican propolis. The current study revealed the presence of antioxidant, antimicrobial, and cytotoxic phytochemicals [galangin (**3**); ferulic acid (**10**); syringic acid (**11**); and caffeic acid (**12**)] in EEP. It is concluded that EEP can be a potential addition in pharmaceutical products for the improvement of human health by contributing in the antioxidant defense system fighting against the production of free radicals. México, being a megadiverse country, has numerous numbers of propolis differing in chemical composition. However, unfortunately it is still unexplored.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-3921/9/1/70/s1, Figure S1: Flavonoids isolated from EEP GUA-4; Figure S2: Analytical ion current chromatogram (AIC) of propolis

GUA-4; Figure S3: Major volatile compounds of EEP GUA-4; Table S1: 1H-RMN data of the flavonoids isolated from Mexican propolis.

**Author Contributions:** J.G.-P. performed the phytochemical study; J.F.R.-C. conceived and designed the phytochemical experiments and wrote the paper; J.M.P.-R. conceived and designed the in vitro experiments; A.K.-P.reviewed of the manuscript and contributed with in vitro experiments; G.D.-R. contributed with the antimicrobial assays; J.P.-C. reviewed the manuscript and contributed with in vitro experiments; B.E.R.-C. reviewed of the manuscript and contributed with in vitro experiments. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by CONACyT CB-252006 and College of Chemistry, National Autonomous University of Mexico under the PAIP 5000-9138 Fellowship Scheme.

**Acknowledgments:** We are in debt to Médico Veterinario Zootecnista. Ánge<sup>l</sup> <sup>L</sup>ópez-Ramírez for technical assistance in propolis recolection. Jessica Granados Pineda is a doctoral student from the Programa de Doctorado en Ciencias Químicas, Universidad Nacional Autónoma de México (UNAM), Facultad de Química, and recieved a CONACyT fellowship # 273461. The authors wish to thank the technical assistance of Georgina Duarte-Lisci and Juan Rojas-Moreno.

**Conflicts of Interest:** The authors declare no conflict of interest.
