Allium vegetables and organosulfur compounds: do they help prevent cancer?

Abstract

The Allium genus includes approximately 500 species, the most widely used of which are onions (Allium cepa), garlic (Allium sativum), leeks (Allium porrum), chives (Allium schoenoprasum), and shallots (Allium ascalonicum). Garlic is widely cultivated and consumed worldwide, and its beneficial effects have been known for thousands of years. It has been considered to increase longevity and to confer stamina and physical strength, and it has been used empirically as a vermifuge, antiseptic, antimicrobic, antipyretic, and analgesic. The scientific community has now become interested in the pharmacologic properties of Allium vegetables and their chemical constituents, particularly with regard to their effects on the cardiovascular system and in the prevention of cancer. Garlic has antihypertensive and antiarrythmic properties and exerts an antithrombotic effect through fibrinolytic activity and the reduction of platelet aggregation. Ingestion of garlic has also been reported to lower the concentration of triglycerides, cholesterol, and low-density lipoproteins and to increase the concentration of high-density lipoproteins in blood. These findings suggest that garlic has a preventive effect against atherosclerosis and its complications, including stroke, myocardial infarction, and thrombotic disorders. The findings in relation to cancer prevention that have been accumulated over the last 20 years are summarized here.We performed a systematic Medline search of the published literature on epidemiologic studies involving the relationship between consumption of Allium vegetables-garlic, onions, and leeks-and neoplasms/tumors. For the animal studies and for studies on mechanisms of action, we conducted searches for review articles. These lists of references were then updated using references from review papers and original research articles. Active Compounds in Allium VegetablesFresh garlic contains water, carbohydrates, proteins, fiber, and fat, as well as essential amino acids, vitamins, and minerals. When garlic is cut, chopped, or crushed, the clove's membrane is disrupted and S-allylcysteine sulfoxide (an odorless compound called alliine) is transformed enzymatically into allicin by alliinase (1). Allicin is responsible for the typical odor of garlic, but it is unstable and converts readily into mono-, di-, and trisulfides and other compounds such as ajoene. Onions mainly contain S-propenylcysteine sulfoxide (1), but also other sulfoxides, including S-propylcysteine sulfoxide and S-methylcysteine sulfoxide (2). S-Propenylcysteine sulfoxide, positional isomer of alliin, is called lacrimatory precursor, because it is tranformed by alliinase into the lacrimatory factor propanethial S-oxide. The lacrimatory factor is highly reactive and hydrolyzes to propionaldehyde, sulfuric acid, and hydrogen sulfide; it is also the precursor of several sulfur derivatives. Organosulfur compounds present in Allium vegetables, which are either lipid or water soluble (Table 1), are considered responsible for the beneficial effects of these...

Pikuni-Blackfeet traditional medicine: Neuroprotective activities of medicinal plants used to treat Parkinson’s disease-related symptoms

“…has been used as a stimulant (Hamel, 1975) (Supplementary Table 3). We note that similar pro-health effects have been reported for different Allium species, likely because these species have a similar chemical content characterized by high levels of organosulfur compounds (Bianchini and Vainio, 2001; Rahman, 2003; Rose et al, 2005). Amelanchier alnifolia has febrifuge and tonic properties and is used as an adjuvant for medicinal preparations (Leighton, 1985; Turner, 1980) (Supplementary Table 3).…”

Garlic intake and gastric cancer risk: Results from two large prospective US cohort studies

“…Among the hundreds of species in the Allium genus, garlic ( Allium sativum ) is particularly well-known for its beneficial effects and has been widely consumed, cultivated, and researched worldwide for centuries. To date, the evidence for inverse association between garlic intake and gastric cancer risk was based primarily on the results from case-control studies 5, 7–10 . Compared to cohort studies, case-control studies are more prone to biases such as recall bias, selection bias, and reverse causation.…”

“…At present, we have limited knowledge on the stability of the organosulfur compounds during cooking 7 . An experimental study suggested that cooked garlic no longer has beneficial effects, at least in carcinogenesis 31 .…”

“…An inverse association between garlic intake and gastric cancer was derived mainly from case-control studies 5, 7–10 . A recent meta-analysis including 12 case-control studies estimated pooled relative risk (RR) of 0.60 (95% confidence interval, CI, 0.47 to 0.76) for the highest versus lowest category of garlic intake 10 .…”

Role of hydrogen sulfide in skeletal muscle biology and metabolism

“…For instance, gut bacteria were also reported to engender significant amount of H 2 S [5]. Furthermore, human diet that is rich in organosulfur compounds such as garlic, onions, leeks and chives have been reported to contribute to H 2 S pool and to exert significant influence on the metabolic state and hypertension [6]. Nonetheless, regulated H 2 S production at defined tissue milieu and sub-cellular spaces occurs through specific enzymes.…”