Amygdalin

Background: Amygdalin is a cyanogenic glycoside which is described as a naturally occurring anticancer agent. Current review highlights apoptosis-inducing attributes of amygdalin towards different cancers and its potential application as an anti-cancer agent in cancer therapy. Method: Data about amygdalin was retrieved from all major scientific databases i.e., PubMed, ScienceDirect, Google Scholar, Scopus and Medline by using combination of keywords like amygdalin, apoptosis, laetrile, vitamin B- 17, pro-apoptotic proteins, anti-apoptotic proteins, hydrogen cyanide, mechanism of action of amygdalin and amygdalin therapy on humans. However, no specific time frame was followed for collection of data. Results: Data collected from already published articles revealed that apoptosis is a central process activated by amygdalin in cancer cells. It is suggested to stimulate apoptotic process by upregulating expression of Bax (proapoptotic protein) and caspase-3 and downregulating expression of Bcl-2 (anti-apoptotic protein). It also promotes arrest of cell cycle in G0/G1 phase and decrease number of cells entering S and G2/M phases. Thus, it is proposed to enhance deceleration of cell cycle by blocking cell proliferation and growth. Conclusion: The current review epitomizes published information and provides complete interpretations about all known anti-cancer mechanisms of amygdalin, possible role of naturally occurring amygdalin in fight against cancer and mistaken belief about cyanide toxicity causing potential of amygdalin. However, well-planned clinical trials are still needed to be conducted to prove effectiveness of this substance in vivo and to get approval for human use.

Amygdalin (d-Mandelonitrile 6- O -β-d-glucosido-β-d-glucoside) is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity. The aim of this review is to present the current state of knowledge on the sources, toxicity and anticancer properties of amygdalin, and analytical methods for its determination in plant seeds.

Ethnopharmacological relevance: Amygdalin is commonly distributed in plants of the Rosaceae, such as peach, plum, loquat, apple and bayberry, but most notably in the seeds (kernels) of apricot almonds. As a naturally aromatic cyanogenic compound, it has long been used in Asia, Europe and other regions for the treatment of various diseases including cough, asthma, nausea, leprosy and leukoderma. Importantly, in recent years, an increasing attention has been paid to its antitumor effect. Aim of the study: The paper aims to review the pharmacological activities and toxicological effects of amygdalin and provide a reference and perspective for its further investigation. Methods: Electronic databases including the Web of Science, Cochrane Library, PubMed, EMBASE, the Chinese Biological Medicine Database, China National Knowledge Infrastructure, Wanfang database and VIP information database were searched up to November 2019 to identify eligible studies. A meticulous review was performed, an in-depth analysis on the pharmacological activity and toxicology of amygdalin was conducted, and perspectives for future research were also discussed. Results: A total of 110 papers about in vitro/in vivo studies on amygdalin have been reviewed. Analysis on the data suggested that this compound presented pharmacological activities of anti-tumor, anti-fibrotic, anti-inflammatory, analgesic, immunomodulatory, anti-atherosclerosis, ameliorating digestive system and reproductive system, improving neurodegeneration and myocardial hypertrophy, as well as reducing blood glucose. In addition, studies revealed that amygdalin's toxicity was caused by its poisonous decomposite product of benzaldehyde and hydrogen cyanide after oral ingestion, toxicity of intravenous administration route was far less than the oral route, and it can be avoidable with an oral dose ranging from 0.6 to 1 g per day. Conclusion: This paper has systematically reviewed the pharmacology and toxicology of amygdalin and provided comprehensive information on this compound. We hope this review highlights some perspectives for the future research and development of amygdalin.