Mechanism of Action of Limonene in Tumor Cells: A Systematic Review and Meta-Analysis.

BACKGROUND: Cancer is a complex, multifactorial disease, and a major public health problem, as it is a leading cause of morbidity and mortality worldwide. Although treatments have significantly improved, still more effective drugs are searched. One source for these drugs is natural products (NPs). One NP that has shown anticancer activity is Limonene. However, the mechanisms of limonene's antiproliferative, anticancer and antineoplastic activity are not fully understood. OBJECTIVE: The objective of this study is to undertake a systematic review and meta-analysis of the literature on this subject. METHODS: A comprehensive literature search was performed using the Scopus, MEDLINE-PubMed, Web of Science, and Science Direct databases using the keywords: "limonene", "cancer", "neoplasm", and "tumor". The inclusion criteria were: in vivo and in vitro studies on the use of limonene in cancer published in English, Portuguese and Spanish until December 2019. Review articles, meta-analyses, abstracts, conference papers, editorials/ letters and case reports were excluded. RESULTS: The search identified 3568 articles, of which, 126 were selected for full reading, with 11 papers meeting the review criteria. Six more papers were added from the references of the initial 11 texts, giving a total of 17 papers. There was a high level of agreement in inclusion/exclusion (Kappa index > 80%). The risk of bias in the texts was shown to be high. CONCLUSION: The meta-analysis suggests that limonene acts mainly on tumor regression induced apoptosis and is a promising natural product for use in the treatment of several types of cancer.

Anti-Inflammatory Activity of Limonene in the Prevention and Control of Injuries in the Respiratory System: A Systematic Review.

INTRODUCTION: The pulmonary inflammatory response results from exposure to injurious factors and is associated with oxidative stress, which intensifies the pathological reaction. In this context, limonene, a monoterpene found in citrus fruits, can be a therapeutic alternative for the treatment of this pathology, as it presents known anti-inflammatory and antioxidant actions. OBJECTIVE: The purpose of this article is to provide an overview of the anti-inflammatory activity of limonene and its capacity to prevent and control respiratory system injuries. SEARCH STRATEGY: A comprehensive literature search of the Cochrane, Scopus, MEDLINE-PubMed, Web of Science, and Lilacs databases was performed using the keywords: "limonene", "lung", "pulmonary", "airway", "trachea", "lung injury", "respiratory system", "respiratory tract diseases". SELECTION CRITERIA: Studies on the use of limonene in disorders of the respiratory system, published until August 2019, were included. Those that did not use limonene alone or treated lesions in different systems other than the respiratory system, without targeting its anti-inflammatory action were excluded. In addition, review articles, meta-analyses, abstracts, conference papers, editorials/letters and case reports were also excluded. RESULTS: Of the 561 articles found, 64 were in the Cochrane database, 235 in Scopus, 99 in Web of science, 150 in PubMed and 13 in Lilacs. After completing the systematic steps, 25 articles were selected for full reading, after which 7 papers remained in the review. An article was added after a manual literature search, resulting in a total of 8 papers. There was a high level of agreement on inclusion/exclusion among the researchers who examined the papers (Kappa index > 88%). CONCLUSION: Limonene has effective anti-inflammatory activity in both preventing and controlling respiratory system injuries.