Constituents Of Citrus Fruits Research Articles

Pharmacological Significance of Hesperidin and Hesperetin, Two Citrus Flavonoids, as Promising Antiviral Compounds for Prophylaxis Against and Combating COVID-19

Hesperidin and hesperetin are flavonoids that are abundantly present as constituents of citrus fruits. These compounds have attracted attention as several computational methods, mostly docking studies, have shown that hesperidin may bind to multiple regions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (spike protein, angiotensin-converting enzyme 2, and proteases). Hesperidin has a low binding energy, both with the SARS-CoV-2 “spike” protein responsible for internalization, and also with the “PLpro” and “Mpro” responsible for transforming the early proteins of the virus into the complex responsible for viral replication. This suggests that these flavonoids could act as prophylactic agents by blocking several mechanisms of viral infection and replication, and thus helping the host cell to resist viral attack.

Stachydrine Mediates Rapid Vascular Relaxation: Activation of Endothelial Nitric Oxide Synthase Involving AMP-Activated Protein Kinase and Akt Phosphorylation in Vascular Endothelial Cells.

Stachydrine (STA) is a constituent of citrus fruits and Leonurus heterophyllus Sweet. In the present study, we established that STA caused acute endothelium-dependent relaxation. The vascular action of STA was mediated by nitric oxide (NO) via cyclic guanosine monophosphate. Mechanistically, STA activated AMP-activated protein kinase (AMPK), protein kinase B/Akt, and endothelial NO synthase (eNOS) in vascular endothelial cells (ECs). AMPK inhibition by compound C blocked STA-induced Akt/eNOS phosphorylation, suggesting that AMPK is the upstream of Akt and eNOS. Inhibition of Akt by MK2206 blocked STA-stimulated eNOS phosphorylation without altering AMPK phosphorylation. Furthermore, we showed that STA activated AMPK via the induction of liver kinase B1 phosphorylation. These results indicated that STA can induce eNOS phosphorylation and vasorelaxation by regulating the interplay between AMPK and Akt pathways in ECs. These findings further highlighted the potential of STA as a nutritional factor in the beneficial effects of fruit intake in preventing the endothelial dysfunction-related metabolic cardiovascular diseases.

Abstract 3269A: 2-Hydroxyflavanone: A novel estrogen receptor alpha downregulator with potent antitumor effect in breast cancer

Abstract Breast cancer (BC) remains one of the major causes of cancer deaths in women. 2Hydroxyflavanone (2HF), a constituent of citrus fruits, inhibits growth of human breast cancer cell lines in culture. The present study was undertaken to determine in vivo efficacy of 2HF against MDAMB231 human breast cancer xenografts. The 2HF administration retarded growth of MDAMB231 cells subcutaneously implanted in female nude mice without causing weight loss or any other side effects. The 2HF mediated suppression of MDAMB231 xenograft growth correlated with reduced cell proliferation as revealed by immunohistochemical analysis for Ki67 expression. Analysis of the vasculature in the tumors from 2HF treated mice indicated smaller vessel area compared with control tumors based on immunohistochemistry for angiogenesis marker CD31. The 2HF mediated inhibition of angiogenesis in vivo correlated with downregulation of vascular endothelial growth factor (VEGF) level in the tumor. Consistent with these results, 2HF treatment suppressed cell cycle regulators levels in cultured MDAMB231 cells. Moreover, the 2HF treated MDAMB231 cells exhibited reduced capacity for migration compared with vehicle-treated control cells. In addition, 2HF administration elicits apoptotic response as judged by annexin V and PI staining and TUNEL assay. 2HF treatment reduced the levels of ER alpha in ER positive MCF7 breast cancer cells. In conclusion, the present study demonstrates in vivo anticancer efficacy of 2HF against MDAMB231 xenografts in association with reduced cell proliferation and suppression of neovascularization. Our results indicate that 2HF is a promising anticancer agent for breast cancer due to its ability to collectively inhibit major regulators of breast cancer including RLIP76, ER alpha, and HER2. Interestingly, a spontaneously immortalized non-tumorigenic normal human mammary epithelial cell line (MCF10A) is significantly more resistant to 2HF mediated apoptosis compared with breast cancer cells, demonstrating selectivity of 2HF towards malignant breast cells. These preclinical observations merit clinical investigation to determine efficacy of 2HF against human breast cancers. (This work was supported in part by the Department of Defense grant W81XWH 16 1 0641. Funding from the Beckman Research Institute of City of Hope is also acknowledged). Citation Format: Sharad S. Singhal, Shireen Chikara, Lokesh Nagaprashantha, Jyotsana Singhal, David Horne, Sanjay Awasthi. 2-Hydroxyflavanone: A novel estrogen receptor alpha downregulator with potent antitumor effect in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3269A.

Abstract B99: Determinants of aspirin metabolism in healthy individuals

Abstract Regular use of aspirin is associated with lower colon cancer risk. High inter-individual variation in aspirin metabolism has been attributed to several factors, including sex, concomitant use of other drugs or alcohol, urine pH, ethnicity, and variants in metabolizing enzymes involved in glucuronidation of aspirin metabolites [i.e., UDP glucuronosyltransferases (UGT)]. However, little is known about the impact of other exposures, including dietary factors. Dietary constituents of citrus fruits, cruciferous vegetables and soy have been shown to induce UGT. Higher intakes may alter UGT activity and affect the ratio of aspirin metabolites excreted. We evaluated, cross-sectionally, whether urinary excretion of aspirin [ASA] and its metabolites (salicylic acid [SA], salicyluric acid [SUA], salicyluric phonolic glucuronide [SUPG], salicyl acyl and phenolic acid glucuronides [SAG/SPG]) differed by UGT1A6 genotype and dietary factors. Following an oral dose of 650 mg aspirin, healthy men (N=264) and women (N=264), 20–40 years, collected urine over an 8-h period. Participant exclusion criteria included medical history of gastrointestinal, hepatic or renal disorders, and exposure to non-dietary factors known to influence biotransformation enzymes, e.g., medications, excessive alcohol, and smoking. FFQ data were available for 481 participants. Multiple linear regression was used to determine whether there were differences in aspirin metabolism by UGT1A6 genotype, or daily intake of protein, total fruit or vegetable intake, and soy, citrus and cruciferous vegetable intake, adjusted for body mass index (BMI), age, sex, ethnicity, urine volume and pH, and energy intake. There were statistically significant differences in the ratios of metabolites excreted, (specific metabolite/sum of metabolites), between sexes and between ethnic groups. Men excreted more SUA (P<0.001), and women excreted more SA and the glucuronides SAG/SPG (P≤0.001 for all 3). Compared to Caucasians, Asians excreted significantly more ASA, SA and SAG, and less SUA and SUPG (P≤0.03 for all), and African Americans excreted significantly more combined SAG/SPG, and less SUA (P≤0.04 for both). The interaction term for sex*ethnicity was significant for SUPG (P=0.006), with Caucasian men excreting the most, and Asian women excreting the least. Excretion of urinary aspirin metabolites did not differ statistically significantly between UGT1A6 genotypes (UGT1A6 *1/*1, *1/*2, and *2/*2). Increased ASA and decreased SUPG excretion was observed with increased servings of total vegetables (P=0.008 for both), and a trend toward significance with intake of cruciferous vegetables specifically (P=0.05 for both). A corresponding increase in SAG/SPG glucuronides was observed, but was not significant (P=0.40). There were no significant differences in metabolite excretion by soy or citrus fruit intake. Of the factors evaluated, ethnicity and sex were the greatest, albeit modest, contributors to variability in aspirin metabolism (R2=2−13%), whereas UGT1A6 had no effect. Our results also suggest that diet may influence aspirin metabolism, but the effects do not appear to be via glucuronidation. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B99.

Flavonoids and Vitamin E Reduce the Release of the Angiogenic Peptide Vascular Endothelial Growth Factor from Human Tumor Cells

Neoangiogenesis is required for tumor development and progression. Many solid tumors induce vascular proliferation by production of angiogenic factors, prominently vascular endothelial growth factor (VEGF). Because nutrition is a causative factor for tumor prevention and promotion, we determined whether secondary plant constituents, i.e., flavonoids, tocopherols, curcumin, and other substances regulate VEGF in human tumor cells in vitro. VEGF release (concurrent with synthesis) from MDA human breast cancer cells and, for comparison, U-343 and U-118 glioma cells was measured by ELISA. Of 21 compounds tested, 9 showed significant inhibitory activity at 0.1 micromol/L in MDA human breast cancer cells. The rank order of inhibitory potency was naringin > rutin > alpha-tocopheryl succinate (alpha-TOS) > lovastatin > apigenin > genistein > alpha-tocopherol >or= kaempferol > gamma-tocopherol; chrysin and curcumin were inactive except at a concentration of 100 micromol/L. Glioma cells were similarly sensitive, with U343 more than U118, especially for alpha-TOS and tocopherols. Among the tocopherol derivatives, alpha-TOS (0.1 micromol/L) was the most effective in reducing VEGF release. Overall, the glycosylated flavonoids (i.e., naringin, a constituent of citrus fruits, and rutin, a constituent of cranberries) induced the greatest response to treatment at the lowest concentration in MDA human breast cancer cells. Inhibition of VEGF release by flavonoids, tocopherols, and lovastatin in these models of neoplastic cells suggests a novel mechanism for mammary cancer prevention.