In vitro activity evaluation of Lippia alba essential oil against Zika virus

III. Abstract The Zika virus (ZIKV) of the Flaviviridae family is an emerging virus that caused, between 2016 and 2018, serious public health problems in Latin America, affecting neonates with greater severity. The clinical spectrum includes Guillain-Barré syndrome, microcephaly and others neurodegenerative diseases. There is no antiviral treatment or vaccine against this virus, for that reason the antiviral properties of various plants are being studied. Lippia alba , locally known as “Prontoalivio”, is an aromatic shrub of the Verbenaceae family with a wide geographical distribution (especially in South and Central America) and is used in traditional medicine against fever, skin diseases and as a pain reliever. In this study, the antiviral activity of the essential oil of Lippia alba against ZIKV was evaluated in the Vero 76 cell line. Lippia alba was collected in the department of Amazonas, in the rainforest of Peru, and identified in the Museo de Historia Natural of the Universidad Nacional Mayor de San Marcos. The essential oil sample was obtained by steam hydrodistillation. The essential oil showed cytotoxicity to a concentration greater than or equal to 167 μg/mL in the Vero 76 cell line. The antiviral activity of essential oil against ZIKV (previously identified by real-time PCR and propagated in the C6/36 cell line) was evaluated using the plaque reduction test (PRP). The essential oil showed antiviral activity in concentrations from 8.02 μg/mL to 20.88 μg/mL, which represents a range between 59.44% to 85.56% of plaque reduction and may be considered as a candidate for antiviral studies against ZIKV. IV. Author Summary Environmental temperature fluctuations, human activities and vector characteristics increase ZIKV cases worldwide. This neglected disease has been silently affecting people of all ages, generating greater impact on neonates by causing microcephaly and other neurodegenerative diseases. ZIKV vaccines are in phase II trials and there is no antiviral treatment. Nowadays, the study of antiviral plants is gaining strength in the scientific community because they are known to contain chemical compounds that could be drugs candidates. In Peru, there are no antiviral treatments studies reported against Zika virus, this first report is important because it creates a new line of research for future studies of antiviral plant extracts against neglected viral-diseases. Finally, the essential oil of Lippia alba showed antiviral activity against ZIKV in Vero 76 cells, moreover, we intend to carefully isolate and study the chemical compounds as drug candidates in animals trials and possible humans trials. Disclaimer The views expressed in this manuscript are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U.S. Government. Copyright statement Juan Sulca is an employee of the U.S. Government. This work was prepared as part of their official duties. Title 17 U.S.C. § 105 provides that ‘Copyright protection under this title is not available for any work of the United States Government’. Title 17 U.S.C. § 101 defines a U.S. Government work as a work prepared by a military service member or employee of the U.S. Government as part of that person’s official duties.