Identification of compound causing yellow bone discoloration following alpha-glycosyl isoquercitrin exposure in Sprague-Dawley rats

Oral chronic toxicity and carcinogenicity study of alpha-glycosyl isoquercitrin (AGIQ) in Sprague Dawley rats

alpha-Glycosyl isoquercitrin (AGIQ) is a flavonoid that possesses antioxidant and tumor suppressive capabilities and is marketed as a food additive in Japan. The aim of this study was to assess the potential for oral chronic toxicity and carcinogenicity of AGIQ in male and female Sprague Dawley rats following up to 5.0% dietary exposure. In the chronic toxicity study, rats were exposed to AGIQ or vehicle for one year with a 6-month interim termination point; for the carcinogenicity study, rats were treated for 24 months. No signs of AGIQ-related toxicity clinically or histologically were observed for up to one year except for yellow discoloration of bone. In the carcinogenicity study, a statistically significant increase in the incidence of malignant glioma of the brain or spinal cord was observed in female rats exposed to 5.0% AGIQ compared to those exposed to control feed. A Scientific Advisory Panel of experienced neuropathologists reviewed the gliomas (routine stains and glial cell markers) and concluded that the gliomas were a rare, spontaneous, rat-specific neoplasm: malignant microglial tumor. The lesions could not definitively be attributed to AGIQ exposure and have limited implications with respect to predicting human cancer risk.

Enzymatically Modified Isoquercitrin: Production, Metabolism, Bioavailability, Toxicity, Pharmacology, and Related Molecular Mechanisms

Quercetin and its glycosides, such as isoquercitrin or rutin, are among the most ubiquitous flavonoids present in plants. They possess numerous health-promoting properties, whose applicability is, however, limited by poor water solubility and absorption issues. Enzymatically modified isoquercitrin (EMIQ) is an isoquercitrin derivative obtained from rutin via enzymatic transformations that greatly enhance its bioavailability. Due to advantageous reports on its safety and bioactivity, EMIQ is currently gaining importance as a food additive and a constituent of dietary supplements. This review summarizes the thus-far-conducted investigations into the metabolism, toxicity, biological properties, and molecular mechanisms of EMIQ and presents a comprehensive characterization of this valuable substance, which might represent the future of flavonoid supplementation.

Modification of flavonoids: methods and influences on biological activities

Flavonoids are important active ingredients in plant-based food, which have many beneficial effects on health. But the low solubility, poor oral bioavailability, and inferior stability of many flavonoids may limit their applications in the food, cosmetics, and pharmaceutical industries. Structural modification can overcome these shortcomings to improve and extend the application of flavonoids. The study of how to modify flavonoids and the influence of various modifications on biological activity have drawn great interest in the current literature. In this review, the working principles and operating conditions of modification methods were summarized along with their potential and limitations in terms of operational safety, cost, and productivity. The influence of various modifications on biological activities and the structure-activity relationships of flavonoids derivatives were discussed and highlighted, which may give guidance for the synthesis of highly effective active agents. In addition, the safety of flavonoids derivatives is reviewed, and future research directions of flavonoid modification research are discussed.

alpha-Glycosyl Isoquercitrin (AGIQ) and its lack of carcinogenicity in rasH2 mice

alpha-Glycosyl Isoquercitrin (AGIQ), is used in Japan as a food additive and was granted generally recognized as safe (GRAS) status in 2005 (FEMA) and 2007 (FDA). The safety and toxicity information for AGIQ is sparse and therefore, the carcinogenicity potential of AGIQ was examined in the CByB6F1-Tg(HRAS)2Jic (rasH2) model. One hundred female and male rasH2 mice, each, were allocated to one of four designated dose groups; 0 (control)%, 1.5%, 3.0% or 5.0% AGIQ. Animals were administered the diets for six months and an additional 10 females and 10 males, each, were administered a positive control, N-methyl-N-nitrosourea (MNU). Body weights and clinical observations were collected. A full screen necropsy, organ weights, clinical chemistry, urinalysis and histopathology were performed. The positive control animals elicited appropriate responses specific to this strain (rasH2) of mice. There were statistically significant sporadic non-dose-dependent changes in clinical chemistries without corresponding pathological correlation. No microscopic AGIQ-related findings were noted; the range of pathology observations were all considered background findings, either specific to rasH2 mice or common to inbred strains of mice. Therefore, under the study conditions, the no-observed-adverse-effect level (NOAEL) was determined to be more than 5.0% (7215.4 mg/kg BW/day in male mice and 14685.5 mg/kg/day in female mice).

Embryo-fetal developmental toxicity study of alpha-glycosyl isoquercitrin administered orally to New Zealand White rabbits

An embryo-fetal survival and development study was conducted to augment the toxicity database for alpha-glycosyl isoquercitrin (AGIQ), a generally recognized as safe (GRAS) additive and flavor in food and beverages. In Phase I, 24 naturally mated New Zealand white (NZW) female rabbits per group were administered AGIQ by oral gavage at 0, 250, 500, or 1000 mg/kg/day once daily during gestation days 6–28, followed by necropsy. There was no evidence of maternal or fetal toxicity except for equivocal findings of unilateral absent kidney and ureter in one and two unrelated fetuses at 500 and 1000 mg/kg/day, respectively. To more thoroughly assess fetal kidney/ureter development, in Phase II groups of time mated NZW rabbits were administered AGIQ at 0, 500, or 1000 mg/kg/day, under the same conditions as Phase I. No occurrences of absent kidney/ureter were noted in the AGIQ-treated Phase II dams or fetuses; although, one control fetus had unilateral missing kidney/ureter. Given the lack of reproducibility following treatment with AGIQ in Phase II using 48 animals per group, the missing kidney/ureter observations in Phase I were considered unrelated to treatment. Since oral gavage administration of AGIQ to pregnant female NZW rabbits at dose levels of 250, 500, or 1000 mg/kg/day was well-tolerated with no adverse treatment-related effects on the maternal animal, pregnancy, or the developing conceptus, the no-observed-adverse-effect-level (NOAEL) for maternal toxicity and embryo-fetal survival, growth, and development was 1000 mg/kg/day.