Antioxidative, Antiproliferative and Antimicrobial Activities of Phenolic Compounds from Three Myrcia Species
Myrcia bella Cambess., Myrcia fallax (Rich.) DC. and Myrcia guianensis (Aubl.) DC. (Myrtaceae) are trees found in Brazilian Cerrado. They have been widely used in folk medicine for the treatment of gastrointestinal disorders, hemorrhagic and infectious diseases. Few reports have been found in the literature connecting their phenolic composition and biological activities. In this regard, we have profiled the main phenolic constituents of Myrcia spp. leaves extracts by ESI(−)Q-TOF-MS. The main
... stituents found were ellagic acid (M. bella), galloyl glucose isomers (M. guianensis) and hexahydroxydiphenic (HHDP) acid derivatives (M. fallax). In addition, quercetin and myricetin derivatives were also found in all Myrcia spp. extracts. The most promising antioxidant activity, measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, was found for M. fallax extracts (EC 50 8.61 ± 0.22 µg·mL −1 ), being slightly less active than quercetin and gallic acid (EC 50 2.96 ± 0.17 and 2.03 ± 0.02 µg·mL −1 , respectively). For in vitro antiproliferative activity, M. guianensis showed good activity against leukemia (K562 TGI = 7.45 µg·mL −1 ). The best antimicrobial activity was observed for M. bella and M. fallax to Escherichia coli (300 and 250 µg·mL −1 , respectively). In conclusion, the activities found are closely related to the phenolic composition of these plants. Molecules 2018, 23, 986 2 of 12 and Psidium guajava L. (guava), among others. Myrcia is one genus of the Myrtaceae which includes shrubs and small trees, which are described an important source of essential oils, in which monoand sesquiterpenes are predominant. The non-volatile compounds isolated from Myrcia spp. extracts are usually flavonoids, tannins, acetophenone derivatives and triterpenes, which have already been described to possess hypoglycemic, anti-hemorrhagic and antioxidant activities  . The search for phytochemicals has been increased due to their potential use in therapy as antioxidants or anticancer drugs. Among them, phenolic compounds form the major group. The importance of the search for natural antioxidants is highlighted by their action in disposing, scavenging, and suppressing the formation of reactive oxygen species (ROS) or in opposing their actions. Experimental studies have also associated oxidative cellular damage arising from an imbalance between free radical generation and scavenging systems as the primary cause of cardiovascular disease, cancer and aging. They exert different properties such as reducing agents, hydrogen donors, free radical scavengers, singlet oxygen quenchers and metal chelators  . The scavenging of DPPH radicals is widely used for rapid evaluation of the antioxidant activity of different compounds, and the inhibitory effect of tannins and flavonoids against the DPPH radical is well established [3, 4] . Some of the phenolics found in Myrtaceae have already been described as scavengers of free radicals and antioxidants [3, 5] . Some phenolics found in plants are also an alternative therapy against conventionally resistant infections or as new antiseptic agents. Infectious diseases are of great interest in the scientific community because some microorganisms cause severe morbidity and can be lethal. It should be noted that some Myrtaceae extracts, specifically those of M. tomentosa, have already been analyzed as antimicrobial agents  . Typically, polyphenolics and their derivatives from plant extracts are being determined, mainly via chromatographic protocols  . Direct infusion electrospray ionization high resolution mass spectrometry (ESI-HRMS) has been used for this purpose, because does not require exhaustive sampling preparation for analysis. This method allows the identification of complex organic mixtures without prior extraction or separation steps. It is fast, versatile, and sensitive, consumes a low volume of solvent and does not use more elaborate sample preparation protocols which are usually required for chromatographic separation. We have already applied ESI-HRMS with success in the phenolic fingerprinting studies of Stryphnodrendon obovatum extracts  . In this context, we report herein the rapid characterization of the main phenolic compounds from the hydroethanolic extracts of three different Myrtaceae leaves: Myrcia bella Cambess., Myrcia fallax (Rich.) DC. and Myrcia guianensis (Aubl.) DC., using Electrospray Ionization Quadropole Time-of-Flight Mass Spectrometry in negative ion mode (ESI(−)-Q-TOF-MS). A correlation between the compounds identified by ESI(−)-MS and the antioxidant, antiproliferative, and antimicrobial activities was also established after in vitro analysis.