title: Syzygium cumini (L.) Skeels essential oil and its major constituent α-pinene exhibit anti-Leishmania activity through immunomodulation in vitro.
abstract: BACKGROUND
  Syzygium cumini (L.) Skeels (Myrtaceae), commonly known as "jambolão" in Brazil is widely used in folk medicine against leishmaniasis, inflammation, chronic diarrhea, and ulcers. It is one of the most commonly used plants for the treatment of diabetes worldwide. In previous studies, Syzygium cumini was shown to possess antihyperlipidemic and anti-allergic properties, and to exhibit good performance as an antimicrobial agent against bacteria, fungi, and protozoa parasites of the genus Leishmania and Trypanosoma. This study was aimed at evaluating the effects of S. cumini essential oil (ScEO) and its major component α-pinene on Leishmania (Leishmania) amazonensis, as well as their cytotoxicity and possible mechanisms of action.
  
  
  METHODS
  To evaluate the anti-proliferative effect on Leishmania, effects on promastigote and axenic amastigote forms were assessed using tetrazolium salt (MTT) assay. The intramacrophagic amastigotes were exposed to ScEO and α-pinene to determine the survival index. To gain insight into the mechanism of action involved in the effect on the samples, we evaluated the modulation of macrophage activation state by observing structural (phagocytic and lysosomal activities) and cellular (nitric oxide increase) changes. To assess the safety profile of ScEO and α-pinene, murine macrophages and human red blood cells were treated with ScEO and α-pinene and the selectivity index was calculated for each treatment.
  
  
  RESULTS
  α-Pinene was effective against Leishmania amazonensis promastigote forms, with a half-maximal inhibitory concentration (IC50) value of 19.7µg/mL. α-Pinene was more active (IC50 values of 16.1 and 15.6µg/mL against axenic and intracellular amastigotes, respectively) than ScEO (IC50 values of 43.9 and 38.1µg/mL against axenic and intracellular amastigotes, respectively). Our results showed that the anti-Leishmania effects were mediated by immunomodulatory activity, as evidenced by the observed increases in both phagocytic and lysosomal activity, and the elevated NO levels. ScEO and α-pinene exhibited low cytotoxicity against murine macrophages and human erythrocytes. The 50% cytotoxicity concentration (CC50) values for the macrophages in the MTT assay were 614.1 and 425.2µg/mL for ScEO and α-pinene, respectively, while the corresponding half-maximal hemolytic concentration (HC50) values were 874.3 and 233.3µg/mL.
  
  
  CONCLUSIONS
  Taken together, the results demonstrate that ScEO and its major constituent α-pinene have significant anti-Leishmania activity, modulated by macrophage activation, with acceptable levels of cytotoxicity in murine macrophages and human erythrocytes. Further work is warranted, involving more in-depth mechanistic studies and in vivo investigations.
authors.affiliation: Graduate Program in Pharmacology, Medicinal Plants Research Center, Federal University of Piauí, 64049-550 Teresina, PI, Brazil. Electronic address: klinger.antonio@gmail.com.
authors.forename: Klinger Antonio da Franca
authors.initials: KA
authors.lastname: Rodrigues
authors.affiliation: Graduate Program in Pharmacology, Medicinal Plants Research Center, Federal University of Piauí, 64049-550 Teresina, PI, Brazil. Electronic address: layane.valeria@hotmail.com.
authors.forename: Layane Valéria
authors.initials: LV
authors.lastname: Amorim
authors.affiliation: Laboratory of Pharmacognosy II, Department of Pharmacy, Federal University of Maranhão, 65085-580 São Luís, MA, Brazil. Electronic address: cla_noleto@yahoo.com.br.
authors.forename: Clarice Noleto
authors.initials: CN
authors.lastname: Dias
authors.affiliation: Laboratory of Pharmacognosy II, Department of Pharmacy, Federal University of Maranhão, 65085-580 São Luís, MA, Brazil. Electronic address: deniseufma2013@gmail.com.
authors.forename: Denise Fernandes Coutinho
authors.initials: DF
authors.lastname: Moraes
authors.affiliation: Graduate Program in Pharmacology, Medicinal Plants Research Center, Federal University of Piauí, 64049-550 Teresina, PI, Brazil. Electronic address: sa.portela@hotmail.com.
authors.forename: Sabrina Maria Portela
authors.initials: SM
authors.lastname: Carneiro
authors.affiliation: Graduate Program in Pharmacology, Medicinal Plants Research Center, Federal University of Piauí, 64049-550 Teresina, PI, Brazil. Electronic address: famorim@ufpi.edu.br.
authors.forename: Fernando Aécio de Amorim
authors.initials: FA
authors.lastname: Carvalho
mesh_terms: D000818:Animals; D000081008:Bicyclic Monoterpenes; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects; D005260:Female; D006801:Humans; D056747:Immunomodulation / Q000187:drug effects*; D020128:Inhibitory Concentration 50; D007891:Leishmania / Q000166:cytology / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000187:drug effects*; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D039821:Monoterpenes / Q000009:adverse effects / Q000494:pharmacology*; D009822:Oils, Volatile / Q000009:adverse effects / Q000494:pharmacology*; D027842:Syzygium
chemical_list: D000081008:Bicyclic Monoterpenes; D039821:Monoterpenes; D009822:Oils, Volatile; C005451:alpha-pinene
keywords: Anti-Leishmania; Essential oil; Immunomodulatory activity; Syzygium cumini; α-Pinene