Citrus limonoids induce apoptosis in human neuroblastoma cells and have radical scavenging activity

Obacunone represses Salmonella pathogenicity islands 1 and 2 in an envZ-dependent fashion

Obacunone belongs to a class of unique triterpenoids called limonoids, present in Citrus species. Previous studies from our laboratory suggested that obacunone possesses antivirulence activity and demonstrates inhibition of cell-cell signaling in Vibrio harveyi and Escherichia coli O157:H7. The present work sought to determine the effect of obacunone on the food-borne pathogen Salmonella enterica serovar Typhimurium LT2 by using a cDNA microarray. Transcriptomic studies indicated that obacunone represses Salmonella pathogenicity island 1 (SPI1), the maltose transporter, and the hydrogenase operon. Furthermore, phenotypic data for the Caco-2 infection assay and maltose utilization were in agreement with microarray data suggesting repression of SPI1 and maltose transport. Further studies demonstrated that repression of SPI1 was plausibly mediated through hilA. Additionally, obacunone seems to repress SPI2 under SPI2-inducing conditions as well as in Caco-2 infection models. Furthermore, obacunone seems to repress hilA in an EnvZ-dependent fashion. Altogether, the results of the study seems to suggest that obacunone exerts an antivirulence effect on S. Typhimurium and may serve as a lead compound for development of antivirulence strategies for S. Typhimurium.

Production system and storage temperature influence grapefruit vitamin C, limonoids, and carotenoids

Concentrations of grapefruit (cv. 'Rio Red'; Citrus paradisi Macf.) bioactives grown under organic and conventional production systems were evaluated after storage at various temperatures. The first experiment was conducted in November 2008 and the second experiment was conducted in February 2011 using commercial production, processing, and packing procedures. The harvested grapefruits were stored at 23 °C (room temperature) or 9 °C for 4 weeks and analyzed for vitamin C, limonoids, and carotenoids at the end of each week using HPLC. Vitamin C levels were higher in organically grown grapefruits (41.8 mg/100 g) compared to conventionally grown grapefruits (39.2 mg/100 g) at 0 days after harvest in the first experiment. However, production system did not significantly affect vitamin C levels in the second experiment. During storage at room temperature, vitamin C degradation losses ranged from 0.5 to 7% for organically produced grapefruits and from 3 to 18% for conventional grapefruits in both experiments. In the first experiment at harvest, organically produced grapefruits had 77% higher (p ≤ 0.05) nomilin than conventionally produced grapefruits, whereas grapefruits grown under the conventional production system had 2-fold higher lycopene levels compared to organic grapefruits. In the second experiment, both β-carotene and lycopene levels were significantly (p ≤ 0.05) higher in conventionally produced grapefruits than in organic grapefruits. Overall, conventional production significantly increased grapefruit carotenoid levels in both experiments. In general, storage temperature (room temperature and 9 °C) had minimal effects on vitamin C degradation but significant effects on the degradation of carotenoids in the first experiment.

Obacunone and obacunone glucoside inhibit human colon cancer (SW480) cells by the induction of apoptosis

OBJECTIVES

The study was aimed to purify obacunone and obacunone glucoside (OG) from seeds of Marsh White grapefruit and understand the mode of cytotoxicity of limonoids on colon cancer (SW480) cells.

METHODOLOGY

Both limonoids were purified using chromatographic techniques. The structures and purity of limonoids were confirmed by NMR and HPLC analysis, respectively.

RESULTS

Obacunone and OG inhibited SW480 cell proliferation with IC50 values of 97 and 109.7 μM respectively, at 24h. Sequence of events such as decreased ratio of bcl2/bax gene transcription, activation of caspase-3, fragmentation of DNA in cells treated with obacunone and OG demonstrated induction of apoptosis by limonoids. Additionally, higher induction of cytochrome-c in cytosol suggests the activation of intrinsic apoptosis by limonoids. Involvement of apoptosis was also confirmed through expression of bax, bcl2, pro-caspase-3 and caspase-9. Both the limonoids activated p21 and arrested cells at G1 and G2/M phase. Additive activity of proliferation inhibition and activation of caspase-3 by limonoids was observed when combined with camptothecin, demonstrating the induction of apoptosis. In conclusion, both limonoids induced apoptosis by activation of intrinsic apoptosis pathway and activation of p21 leading to arresting cells at G2/M phase of the cell cycle.

Citrus consumption and cancer incidence: the Ohsaki cohort study

Basic research and case-control studies have suggested that citrus consumption may protect against cancer. However, the protective effect has been observed from few prospective studies. This study investigated the association of citrus consumption with cancer incidence among 42,470 Japanese adults in the Ohsaki National Health Insurance Cohort, which covered an age range of 40-79 years, and was followed up from 1995 to 2003 for all-cancer and individual cancer incidence. Citrus consumption was assessed using a self-administered questionnaire. The Cox proportional hazard model was applied to estimate relative risks (RRs) and 95% CIs. During the 323,204 person-years of follow-up, 3,398 cases were identified totally. Citrus consumption, especially daily consumption, was correlated with reduced all-cancer incidence, the RRs were 0.89 (95% CI = 0.80-0.98) for total participants, 0.86 (0.76-0.98) for males and 0.93 (0.79-1.09) for females, as well as multiple cancers at individual sites, especially pancreatic (RR = 0.62, 95% CI = 0.38-1.00) and prostate cancer (RR = 0.63, 95% CI = 0.41-0.97). Joint effect analysis showed a reduced risk of overall cancer existed only for subjects who consumed >or=1 cup green tea/day (RR = 0.83, 95% CI = 0.73-0.93) as well as for males (RR = 0.83, 95% CI = 0.71-0.97) or females (RR = 0.82, 95% CI = 0.68-0.99). These findings suggest that citrus consumption is associated with reduced all-cancer incidence, especially for subjects having simultaneously high green tea consumption. Further work on the specific citrus constituents is warranted, and clinical trials are ultimately necessary to confirm the protective effect.

Citrus limonoids interfere with Vibrio harveyi cell-cell signalling and biofilm formation by modulating the response regulator LuxO

Citrus limonoids are unique secondary metabolites, characterized by a triterpenoid skeleton with a furan ring. Studies have demonstrated beneficial health properties of limonoids. In addition, certain citrus limonoids play a role in plant defence against insect pests. In the present study, five limonoids were purified from sour orange and evaluated for their ability to inhibit cell-cell signalling. The purified limonoids were tested for their ability to interfere with cell-cell signalling and biofilm formation in Vibrio harveyi. Isolimonic acid, deacetylnomilinic acid glucoside and ichangin demonstrated significant inhibition of autoinducer-mediated cell-cell signalling and biofilm formation. Furthermore, isolimonic acid and ichangin treatment resulted in induced expression of the response regulator gene luxO. In addition, luxR promoter activity was not affected by isolimonic acid or ichangin. Therefore, the ability of isolimonic acid and ichangin to interfere with cell-cell signalling and biofilm formation seems to stem from the modulation of luxO expression. The results suggest that isolimonic acid and ichangin are potent modulators of bacterial cell-cell signalling.

In vivo induction of phase II detoxifying enzymes, glutathione transferase and quinone reductase by citrus triterpenoids

Background

Several cell culture and animal studies demonstrated that citrus bioactive compounds have protective effects against certain types of cancer. Among several classes of citrus bioactive compounds, limonoids were reported to prevent different types of cancer. Furthermore, the structures of citrus limonoids were reported to influence the activity of phase II detoxifying enzymes. The purpose of the study was to evaluate how variations in the structures of citrus limonoids (namely nomilin, deacetyl nomilin, and isoobacunoic acid) and a mixture of limonoids would influence phase II enzyme activity in excised tissues from a mouse model.

Methods

In the current study, defatted sour orange seed powder was extracted with ethyl acetate and subjected to silica gel chromatography. The HPLC, NMR and mass spectra were used to elucidate the purity and structure of compounds. Female A/J mice were treated with three limonoids and a mixture in order to evaluate their effect on phase II enzymes in four different tissues. Assays for glutathione S-transferase and NAD(P)H: quinone reductase (QR) were used to evaluate induction of phase II enzymatic activity.

Results

The highest induction of GST against 1-chloro-2,4-dinitrobenzene (CDNB) was observed in stomach (whole), 58% by nomilin, followed by 25% isoobacunoic acid and 19% deacetyl nomilin. Deacetyl nomilin in intestine (small) as well as liver significantly reduced GST activity against CDNB. Additionally isoobacunoic acid and the limonoid mixture in liver demonstrated a significant reduction of GST activity against CDNB. Nomilin significantly induced GST activity against 4-nitroquinoline 1-oxide (4NQO), intestine (280%) and stomach (75%) while deacetyl nomilin showed significant induction only in intestine (73%). Induction of GST activity was also observed in intestine (93%) and stomach (45%) treated with the limonoid mixture. Finally, a significant induction of NAD(P)H: quinone reductase (QR) activity was observed by the limonoid mixture in stomach (200%). In addition, the deacetyl nomilin treatment group displayed an increase in QR activity in liver (183%) and intestine (22%).

Conclusion

The results of the present study suggests that, dietary intake of citrus limonoids may provide a protective effect against the onset of various cancers by inducing the activity of certain phase II detoxifying enzymes in specific organs.

Apigenin and naringenin suppress colon carcinogenesis through the aberrant crypt stage in azoxymethane-treated rats

Epidemiological evidence suggests that a diet abundant in fruits and vegetables may protect against colon cancer. Bioactive compounds, including flavonoids and limonoids, have been shown to possess antiproliferative and antitumorigenic effects in various cancer models. This experiment investigated the effects of four citrus flavonoids and one limonoid mixture at the promotion stage of chemically induced colon cancer in rats. Male Sprague-Dawley rats (n = 10 rats/group) were randomly allocated to one of six diets formulated to contain 0.1% apigenin, 0.02% naringenin, 0.1% hesperidin, 0.01% nobiletin, 0.035% limonin glucoside/obacunone glucoside mixture or a control diet (0% flavonoid/limonoid). Rats received experimental diets for 10 weeks and were injected with azoxymethane (15 mg/kg) at weeks 3 and 4. Excised colons were evaluated for aberrant crypt foci (ACF) formation, colonocyte proliferation (proliferating cell nuclear antigen assay), apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling assay) and expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) (immunoblotting). When compared with the control diet, apigenin lowered the number of high multiplicity ACF (HMACF >4 aberrant crypts/focus) by 57% (P < 0.05), while naringenin lowered both the number of HMACF by 51% (P < 0.05) and the proliferative index by 32% (P < 0.05). Both apigenin and naringenin increased apoptosis of luminal surface colonocytes (78% and 97%, respectively; P < 0.05) when compared with the control diet. Hesperidin, nobiletin and the limonin glucoside/obacunone glucoside mixture did not affect these variables. The colonic mucosal protein levels of iNOS or COX-2 were not different among the six diet groups. The ability of dietary apigenin and naringenin to reduce HMACF, lower proliferation (naringenin only) and increase apoptosis may contribute toward colon cancer prevention. However, these effects were not due to mitigation of iNOS and COX-2 protein levels at the ACF stage of colon cancer.

Citrus limetta leaves extract antagonizes the hypertensive effect of angiotensin II

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus limetta Risso (Rutaceae) is widely used in Mexico for healing purposes, among them as antihypertensive treatment.

AIM OF THE STUDY

To assess the antihypertensive effect of C. limetta leaves as one of its ethnomedical uses.

MATERIALS AND METHODS

The acute response of blood pressure to angiotensin II administration was measured in mice. Additionally, the acute oral toxicity profiles were determined.

RESULTS

The findings of the current investigation showed that different concentrations of the aqueous extract prevented the raise of systolic blood pressure (p< or =0.001 vs. vehicle), diastolic blood pressure (p< or =0.0002 vs. vehicle) and mean blood pressure (p< or =0.0000 vs. vehicle); with a dose dependent effect for diastolic pressures at 125-500mg/kg dosages. The 500 and 1000mg/kg doses inhibited the action of Ang II in similar extent to telmisartan. Toxic signs or deaths were not observed in mice treated at 2000mg/kg of C. limetta extract.

CONCLUSIONS

All doses of C. limetta aqueous extract, used in this assay, were safe and effective.

Bioactive compounds from sour orange inhibit colon cancer cell proliferation and induce cell cycle arrest

Epidemiological studies suggest that dietary limonoids and phytosterols offer protection from certain types of cancers. Potential cancer preventive constituents of sour orange (Citrus aurantium L.) were isolated and identified from ethyl acetate extract. The structures of the compounds were identified by one-dimensional (1H or 13C) and two-dimensional (1H-H and 1H-13C) nuclear magnetic resonance experiments as limonexic acid and beta-sitosterol glucoside (SG). The identified compounds were tested for the potential inhibition of human colon cancer cell (HT-29) proliferation, apoptosis, and also noncancerous cells (COS-1). Cell proliferation, arrest of the cell cycle, and induction of apoptosis were assessed by MTT assay, flow cytometry, and nuclear staining methods, respectively. The MTT assay indicated that both compounds exhibited significant inhibition at various concentrations. These compounds did not show any toxic effects on noncancerous cells. These compounds caused 4-5-fold increases in the counts of G2/M stage cells at 50 microM, indicating a potential role in cell cycle arrest. These findings support the hypothesis that limonoids and phytosterols are effective apoptosis-promoting agents and incorporation of enriched fractions of these compounds in the diet may serve to prevent colon cancer. To the best of our knowledge, this is the first report of the isolation, identification, and cell proliferation assay for limonexic acid and SG from sour orange.

Bioactive compounds from Mexican lime ( Citrus aurantifolia ) juice induce apoptosis in human pancreatic cells

Lime (Citrus aurantifolia Swingle) is one of the major citrus fruits and widely consumed, but there is limited evidence about its health-promoting properties. Hence, an investigation was conducted to understand the chemopreventive effects of lime juice on pancreatic cancer cells and the possible mechanism for induction of apoptosis using Panc-28 cells. Freeze-dried lime juice was extracted with different solvents, such as chloroform, acetone, MeOH, and MeOH/water (8:2). The chloroform extract showed the highest (85.4 and 90%) radical-scavenging activity by 1,1-diphenyl-2-picryl hydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) methods at 624 microg/mL, whereas the MeOH/water extract showed the lowest (<20%) activity. The active components were identified by high-performance liquid chromatography (HPLC) using a C-18 column as rutin, neohesperidin, hesperidin, and hesperitin. Furthermore, the limonoids identified are limonexic acid, isolimonexic acid, and limonin. All of the extracts of lime juice inhibited Panc-28 cancer cell growth. The MeOH extract exhibited the maximum activity, with an IC50 value of 81.20 microg/mL after 72 h. The inhibition of Panc-28 cells was in the range of 73-89%, at 100 microg/mL at 96 h. The involvement of apoptosis in induction of cytotoxicity was confirmed by expression of Bax, Bcl-2, casapase-3, and p53. The results of the present study clearly indicate that antioxidant activity is proportionate to the content of flavonoids and proliferation inhibition ability is proportionate to the content of both flavonoids and limonoids.

Feeding orange pulp improved bone quality in a rat model of male osteoporosis

Oxidative stress and inflammation have been linked to bone loss. We evaluated the effects of feeding orange pulp (OP), a source of vitamin C and flavonoids, on bone quality in a rat model of male osteoporosis. One-year-old retired breeder rats (n = 43) were orchidectomized (ORX) or sham-operated (SHAM). Three days postsurgery, ORX rats were randomly assigned to treatments: ORX or ORX with 2.5% OP, 5% OP, or 10% OP. Diets were isonitrogenous, isocaloric, modified AIN-93M diets with equal fiber content. All ORX rats were fed for 4 months to the mean food intake of the SHAM group. At the end of the study blood, urine and bone samples were collected. Plasma antioxidant capacity and urinary deoxypyridinoline (DPD) were determined. Bone density, structure, and strength were assessed using dual energy X-ray absorptiometry, microcomputed tomography, and finite element analyses. ORX decreased (P < .05) antioxidant status, while OP as low as 2.5% maintained the antioxidant capacity of ORX rats comparable to that of the SHAM group. Cortical thickness at the tibial midshaft was significantly decreased by ORX and increased by OP, and urinary DPD was significantly increased by ORX and decreased by OP. In fourth lumbar trabecular cores, ORX rats had significantly reduced bone volume fraction, connectivity density, and trabecular number and increased trabecular separation. OP significantly increased bone volume fraction and trabecular number and decreased trabecular separation in ORX rats. Improvements due to OP in microarchitectural properties of vertebral bones and in cortical thickness of long bones were subtle but significant. The consistently negative impacts of ORX on bone density, structure, and strength parameters confirm the previously reported importance of testosterone for bone.

Pyrogallol inhibits the growth of human pulmonary adenocarcinoma A549 cells by arresting cell cycle and triggering apoptosis

Pyrogallol (PG) is a polyphenol compound and has been known to be an O(2)(*-) generator. We evaluated the effects of PG on the growth of human pulmonary A549 cells in relation to the cell cycle and apoptosis. Treatment with 50 or 100 microM PG significantly inhibited the cell growth of A549 for 72 h. DNA flow cytometric analysis indicated that PG slightly induced a G1 phase arrest of the cell cycle at 24 or 48 h, but did not induce the specific cell cycle arrest at 72 h. Intracellular GSH depletion was observed in PG-treated cells. PG induced apoptosis in A549 cells, as evidenced by sub-G1 cells, annexin V staining cells, and the loss of mitochondrial membrane potential (DeltaPsi(m)). The intracellular ROS (reactive oxygen species) level including O(2)(*-) increased in PG-treated A549 cells at 24 and 48 h, and persisted at 72 h. The changes in GSH as well as ROS levels by PG affected the cell viability in A549 cells. In conclusion, PG inhibited the growth of human pulmonary A549 cells by inducing cell cycle arrest as well as triggering apoptosis.

Citrus bioactive compounds improve bone quality and plasma antioxidant activity in orchidectomized rats

BACKGROUND

We reported that citrus consumption improves bone quality in orchidectomized male rats. In the present study, effects of feeding citrus bioactive compounds and crude extract on bone quality in orchidectomized rats were evaluated.

METHODS

Seventy 90-days-old male rats were randomly assigned to five groups for 60 days of feeding study. The treatment groups were SHAM-control, orchidectomy (ORX), ORX+crude extract, ORX+limonin, and ORX+naringin. At termination, animals were euthanized, blood was collected for the plasma antioxidant status. Bone resorption and bone formation markers in the blood and urine were evaluated. Bone quality in the femur and the 5th lumbar and the total calcium concentration in the bones and excreta were evaluated.

RESULTS

Orchidectomy lowered (p<0.05) plasma antioxidant capacity, bone quality, and bone calcium; elevated (p<0.05) TRAP, deoxypyridinoline (DPD), and calcium excretion; and did not change the plasma IGF-I in comparison to the SHAM group. The citrus crude extract or the purified bioactive compounds increased (p<0.05) the plasma antioxidant status, plasma IGF-I, and bone density, preserved (p<0.05) the concentration of calcium in the femur and in the 5th lumbar, and numerically improved bone strength. The crude extract and the bioactive compounds decreased (p<0.05) fecal excretion of calcium, numerically lowered the urinary excretion of calcium, and suppressed (p<0.05) the plasma TRAP activity without affecting (p>0.1) urinary excretion of DPD in comparison to the ORX group.

CONCLUSIONS

Potential benefit of the citrus crude extract and its bioactive compounds on bone quality appears to preserve bone calcium concentration and increase antioxidant status.

Vitamin C and the Role of Citrus Juices as Functional Food

The literature on the content and stability of vitamin C (ascorbic acid, AA) in citrus juices in relation to industrial practices is reviewed. The role of vitamin C from citrus juices in human diet is also reviewed. Citrus fruits and juices are rich in several types of bioactive compounds. Their antioxidant activity and related benefits derive not only from vitamin C but also from other phytochemicals, mainly flavonoids. During juice processing, temperature and oxygen are the main factors responsible for vitamin C losses. Nonthermal processed juices retain higher levels of vitamin C, but economic factors apparently delay the use of such methods in the citrus industry. Regarding packing material, vitamin C in fruit juice is quite stable when stored in metal or glass containers, whereas juice stored in plastic bottles has a much shorter shelf-life.

The limiting step for vitamin C absorption in humans is transcellular active transport across the intestinal wall where AA may be oxidized to dehydroascorbic acid (DHAA), which is easily transported across the cell membrane and immediately reduced back to AA by two major pathways. AA bioavailability in the presence of flavonoids has yielded controversial results. Whereas flavonoids seem to inhibit intestinal absorption of AA, some studies have shown that AA in citrus extract was more available than synthetic ascorbic acid alone. DHAA is reported to possess equivalent biological activity to AA, so recent studies often consider the vitamin C activity in the diet as the sum of AA plus DHAA. However, this claimed equivalence should be carefully reexamined.

Humans are one of the few species lacking the enzyme (L-gulonolactone oxidase, GLO) to convert glucose to vitamin C. It has been suggested that this is due to a mutation that provided a survival advantage to early primates, since GLO produces toxic H2O2. Furthermore, the high concentration of AA (and DHAA) in neural tissues could have been the key factor that caused primates (vertebrates with relative big brain) to lose the capacity to synthesize vitamin C.

Oxidative damage has many pathological implications in human health, and AA may play a central role in maintaining the metabolic antioxidant response. The abundance of citrus juices in the Mediterranean diet may provide the main dietary source for natural vitamin C.

Influence of electron-beam irradiation on bioactive compounds in grapefruits ( Citrus paradisi Macf.)

Phytochemical levels in fruits and vegetables can be affected by several postharvest factors. In the present study, the effect of electron-beam (E-beam) irradiation was studied on grapefruit bioactive compounds. 'Rio Red' and 'Marsh White' grapefruits were irradiated with E-beam at 0, 1.0, 2.5, 5.0, and 10.0 kGy. Changes of various bioactive compounds, such as vitamin C, flavonoids, carotenoids, furocoumarins, and limonoids, were measured. The acidity decreased slightly with an increasing E-beam dose, whereas the total soluble solids were increased. Irradiation did not affect the vitamin C content at 1 kGy; however, doses beyond 1 kGy significantly reduced the vitamin C content. Lycopene and beta-carotene did not change significantly from the irradiation. Lycopene levels decreased as the E-beam dose increased, while the beta-carotene content slightly increased. Dihydroxybergamottin levels exhibited a decreasing trend, while the bergamottin content did not change. Naringin, a major flavonoid of grapefruit, showed a significant increase over the control at 10 kGy in both 'Rio Red' and 'Marsh White'. Nomilin continued to decrease with an increasing dose of E-beam irradiation, while limonin levels remained the same at all of the doses. Low-dose E-beam irradiation has very little effect on the bioactive compounds and offers a safe alternative to existing postharvest treatments for the disinfection and decontamination of grapefruits.

Grapefruit juice modulates bone quality in rats

Hypogonadism and oxidative stress increase the risk for developing osteoporosis. The objective of this research was to evaluate the efficacy of drinking grapefruit juice on bone quality in orchidectomized (ORX) and non-ORX rats. Fifty-six 90-day-old male Sprague-Dawley rats were equally divided into four groups--non-ORX rats (sham), sham + grapefruit juice, ORX, and ORX + grapefruit juice--and treated for 60 days. Thereafter, all rats were sacrificed to determine the plasma antioxidant status, insulin-like growth factor I (IGF-I), and indices of bone turnover, bone quality, and calcium and magnesium concentrations in the bone, urine, and feces. Orchidectomy decreased (P < .05) antioxidant status, bone quality, and bone mineral contents and increased (P < .05) indices of bone turnover, urinary deoxypridinoline, calcium, and magnesium, and fecal calcium excretions. In contrast to the ORX group, ORX rats that drank grapefruit juice had an increase (P < .05) in antioxidant status, bone density, and bone mineral contents, delayed femoral fracture, and slowed down (P < .05) bone turnover rate and tended to have a decrease (P = .08) in urinary deoxypridinoline. In sham-treated animals, drinking grapefruit juice increased (P < .05) bone density and tended to increase the femoral strength. The concentration of IGF-I in the plasma was not affected across treatments. In conclusion, drinking grapefruit juice positively affected bone quality by enhancing bone mineral deposition in ORX rats and by improving bone density in non-ORX rats via an undefined mechanism.

A superoxide anion generator, pyrogallol, inhibits the growth of HeLa cells via cell cycle arrest and apoptosis

We investigated the in vitro effects of pyrogallol on cell growth, cell cycle regulation, and apoptosis in HeLa cells. Pyrogallol inhibited the growth of HeLa cells with an IC(50) of approximately 45 microM. Pyrogallol induced arrest during all phases of the cell cycle and also very efficiently resulted in apoptosis in HeLa cells, as evidenced by flow cytometric detection of sub-G1 DNA content, annexin V binding assay, and DAPI staining. This apoptotic process was accompanied by the loss of mitochondrial transmembrane potential (DeltaPsi(m)), Bcl-2 decrease, caspase-3 activation, and PARP cleavage. Pan-caspase inhibitor (Z-VAD) could rescue some HeLa cells from pyrogallol-induced cell death, while caspase-8 and -9 inhibitors unexpectedly enhanced the apoptosis. When we examined the changes of the ROS, H(2)O(2) or O(2)(*-) in pyrogallol-treated cells, H(2)O(2) was slightly increased and O(2)(*-) significantly was increased. In addition, we detected a decreased GSH content in pyrogallol-treated cells. Only pan-caspase inhibitor showing recovery of GSH depletion and reduced intracellular O(2)(*-) level decreased PI staining in pyrogallol-treated HeLa cells, which indicates dead cells. In summary, we have demonstrated that pyrogallol as a generator of ROS, especially O(2) (*-), potently inhibited the growth of HeLa cells through arrests during all phases of the cell cycle and apoptosis.

Cranberry juice improved antioxidant status without affecting bone quality in orchidectomized male rats

BACKGROUND

We reported that drinking citrus juice improves bone quality in orchidectomized senescent male rats. Because cranberry juice, like citrus, is rich in nutrients and phenolic compounds, beneficial effects of citrus juice might also be seen with cranberry juice. An experiment evaluated effect of drinking cranberry juice on bone quality in orchidectomized rats.

METHODS

Thirty-two 1-year-old male rats were randomized to two groups: a sham-control group (n=8) and an orchidectomized group (n=24). The treatments for the 4 months duration of the study were SHAM, orchidectomy (ORX), ORX+drinking either 27% or 45% cranberry juice concentrate added to drinking water. At the termination of the study, the rats were euthanized, blood was collected for plasma antioxidant status and IGF-I. The femur, tibia and the 4th lumbar were evaluated for bone quality. Total calcium and magnesium concentration in the femurs were also evaluated.

RESULTS

ORX did not affect red blood cell (RBC)-induced hemolysis despite lowering (p<0.05) plasma antioxidant capacity; reduced (p<0.05) plasma IGF-I, femoral density, femoral strength, time-induced femoral fracture, bone mineral content, bone mineral area; numerically (p=0.07) lowered 4th lumbar density; decreased (p<0.05) trabecular connectivity, trabecular number, femoral ash; increased (p<0.05) trabecular separation in comparison to the SHAM group. Drinking cranberry juice increased (p<0.05) plasma antioxidant status, protected RBC against hemolysis, but had no positive effect on bone quality or bone mineral status.

CONCLUSIONS

Cranberry juice increases plasma antioxidant status without affecting bone quality.

Citrus limonoids: analysis, bioactivity, and biomedical prospects

Limonoids are a prominent group of secondary metabolites in citrus fruit. The bitter character of some compounds in this group has historically compromised the quality of citrus fruit and juice. Detecting bitter limonoids in citrus, understanding their origins, and developing methods for their removal from citrus juices have provided the basis for citrus limonoid research. Evaluation of the biological activity of citrus limonoids has indicated the potential of these compounds to improve human health as anticancer, cholesterol-lowering, and antiviral agents. This review chronicles the evolution of citrus limonoid research from defining their participation in citrus bitterness to their potential utilization as important contributors to improving human health and well-being.

Hesperidin inhibits expression of hypoxia inducible factor-1 alpha and inflammatory cytokine production from mast cells

The citrus unshiu peel has been used traditionally as a medicine to improve bronchial and asthmatic conditions or cardiac and blood circulation in Korea, China, and Japan. Here, we report the effects of citrus unshiu peel water extract (CPWE) on the phorbol myristate acetate (PMA)+calcium ionophore A23187-induced hypoxia-inducible factor-1alpha (HIF-1alpha) activation and inflammatory cytokine production from the human mast cell line, HMC-1 cells. We compared CPWE with hesperidin, a common constituent of citrus unshiu. CPWE and hesperidin inhibited the PMA+A23187-induced HIF-1alpha expression and the subsequent production of vascular endothelial growth factor (VEGF). In addition, CPWE suppressed PMA+A23187-induced phosphorylation of the extracellular signal-regulated kinase (ERK). We also show that the increased cytokines interleukin (IL)-1beta, IL-8, and tumor necrosis factor (TNF)-alpha level was significantly inhibited by treatment of CPWE or hesperidin. In the present study, we report that CPWE and hesperidin are inhibitors of HIF-1alpha and cytokines on the mast cell-mediated inflammatory responses.

Inhibition of colon cancer cell growth and antioxidant activity of bioactive compounds from Poncirus trifoliata (L.) Raf

Recently several plant derived natural compounds have been screened for their anticancer activity in order to identify putative compounds with novel structures or mechanism of action. In the present study, fruits of Poncirus trifoliata were extracted with acetone and loaded onto silica gel column chromatography. The column was eluted with different solvents to obtain two bioactive compounds. The purity of compounds was analyzed by HPLC and their structures were identified by 1H and 13C NMR experiments as beta-sitosterol and 2-hydroxy-1,2,3-propanetricarboxylic acid 2-methyl ester (HPCME). beta-Sitosterol, HPCME, and trolox were tested for their antioxidant capacity by oxygen radical absorbance capacity (ORAC) measurement. Further, these compounds were tested for their inhibition of cancer cell proliferation and apoptosis using human colon cancer cell line (HT-29). These results were compared with the corresponding activity on non-cancerous (COS-1 fibroblast) cells. Cell proliferation and induction of apoptosis were determined by MTT assay and nuclear staining. The MTT assay indicated that both the compounds exhibited differential inhibition at various concentrations. Significant arrest of cell growth was observed with beta-sitosterol even at low concentration such as 0.63 microM in 48 h and none of the compounds exerted any apparent cytostatic effects on the non-cancerous COS-1 fibroblast cells. Growth inhibition assay suggested the potential use of bioactive compounds as cancer chemopreventive and therapeutic agents. This is the first report on HPCME isolation and identification from Rutaceae family and beta-sitosterol from P. trifoliata.

Simultaneous determination of citrus limonoid aglycones and glucosides by high performance liquid chromatography

High performance liquid chromatography (HPLC) method has been developed for simultaneous quantification of limonoid aglycones and glucosides on a reversed phase C18 column using a binary solvent system, coupled with diode array detector. Seven limonoids such as limonin, nomilin, isolimonic acid, ichangin, isoobacunoic acid, limonin 17-beta-D glucopyranoside and deacetyl nomilinic acid 17-beta-D glucopyranoside were separated and detected at 210 nm. Furthermore, limonoids were separated, identified and quantified in four varieties of citrus fruits and seeds using developed method. Limonin and limonin glucoside were found to be the predominant limonoid aglycone and glucoside, respectively, in all tested samples. The sensitivity of the method was found to be 0.25-0.50 microg for tested limonoids.

A superoxide anion generator, pyrogallol induces apoptosis in As4.1 cells through the depletion of intracellular GSH content

We investigated the involvement of ROS such as H2O2 and O2*-, and GSH in As4.1 cell death induced by pyrogallol. The intracellular H2O2 levels were decreased or increased depending on the concentration and incubation time of pyrogallol. The levels of O2*- were significantly increased. Pyrogallol reduced the intracellular GSH content. And ROS scavengers, Tempol, Tiron, Trimetazidine and NAC could not significantly down-regulate the production of H2O2 and O2*-. However, these ROS scavengers slightly inhibited apoptosis. Interestingly, Tempol showing the recovery of GSH depletion induced by pyrogallol significantly decreased apoptosis without the significant reduction of intracellular O2*- levels. SOD and catalase did not change the level of H2O2 but decreased the level of O2*-. The inhibition of GSH depletion by these was accompanied with the decrease of apoptosis, as evidenced by sub-G1 DNA content, annexin V staining, mitochondria membrane potential (DeltaPsi(m)) and Western data. In addition, ROS scavengers and SOD did not alter a G2 phase accumulation of the cell cycle induced by pyrogallol. However, catalase changed the cell cycle distributions of pyrogallol-treated cells to those of pyrogallol-untreated cells. In summary, we have demonstrated that pyrogallol potently generates ROS, especially O2*-, in As4.1 JG cells, and Tempol, SOD and catalase could rescue to a lesser or greater extent cells from pyrogallol-induced apoptosis through the up-regulation of intracellular GSH content.

An improved HPLC method for the analysis of citrus limonoids in culture media

Recent studies have shown that citrus limonoids have potential health benefits. However, information on the absorption and metabolism of limonoids in human gastrointestinal (GI) tract is limited. In the present study we have investigated the metabolism of limonin glucoside (LG), the predominant limonoid in citrus by four microorganisms (Enterococcus fecalis, Escherichia coli, Lactobacillus salivarius, and Candida albican) widely present in the human lower GI tract. LG and metabolites in the culture medium were purified using solid phase extraction and analyzed using HPLC using UV detection at 210nm. The identity of LG was further confirmed by electrospray ionization mass spectrometry (ESI-MS). Significant metabolic activity of Escherichia coli and Candida albican on LG was observed. Several unidentified metabolites were also found in the medium. The results of the present study indicated that LG may be metabolized in the intestine by some microbes. Further studies are needed to establish the possible route of LG metabolism in the human system.

Citrus nobiletin suppresses bone loss in ovariectomized ddY mice and collagen-induced arthritis in DBA/1J mice: possible involvement of receptor activator of NF-kappaB ligand (RANKL)-induced osteoclastogenesis regulation

Bone resorption is known to accelerate during the onset of several disorders, including osteoporosis (OP) and rheumatoid arthritis (RA). Some epidemiological surveys have suggested that a high intake of vegetables and fruits has an inverse relation to such disease incidence, though the number of active constituents elucidated thus far is limited. In the present study, we examined the efficacy of various food phytochemicals using two animal models. First, female ddY mice were ovariectomized (OVX) or sham-operated (sham), after which five different compounds (phenethyl isothiocyanate, zerumbone, auraptene, 1'-acetoxychavicol acetate, and nobiletin) were administered separately to OVX mice with a mini-osmotic pump at doses of 0.25 or 0.5 mg/day for 4 weeks, with 17beta-estradiol (E_{2}, 0.03 microg/day) used as a positive control. Nobiletin, in contrast to the other tested phytochemicals, significantly (P<0.05) suppressed the reduction of whole bone mineral density by 61%, which was comparable to or higher than the efficacy of E_{2}. Next, nobiletin given as an i.p. administration at 20 mg/kg of body weight, but not 2 mg/kg, to male DBA/1J mice every 2 days for 12 days led to a marked decrease in type II collagen-induced arthritis by 45% (P < 0.05). Furthermore, the flavonoid (4-50 microM) attenuated receptor activator of nuclear factor kappaB ligand (RANKL)-induced osteoclastogenesis of RAW264.7 cells, as detected by tartarate-resistant acid phosphatase activity and microscopic observations. Of note, nobiletin also suppressed RANKL-activated extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase1/2, and p38 mitogen-activated protein kinase activities, and thereby regulated the promoter activation of nuclear factor kappaB (NFkappaB) and activator protein-1, key transcription factors for differentiation. Together, our results suggest that nobiletin is a promising phytochemical for the prevention or treatment of osteoclastogenesis-related disorders, including OP and RA, with reasonable action mechanisms.

Antiproliferative Effects of Citrus Limonoids Against Human Neuroblastoma and Colonic Adenocarcinoma Cells

Limonoids, a family of triterpenoids with putative anticancer properties, occur in fruits as glucosides and aglycones. Both highly purified forms were isolated from seeds and molasses of citrus fruits and tested for toxic effects against two human cancer cell lines, SH-SY5Y neuroblastoma and Caco-2 colonic adenocarcinoma, and a noncancerous mammalian epithelial Chinese hamster ovary (CHO) cells. Viability, as quantified by 3-[4,5-dimethylthiazol- 2-yl]-2,5-diphenyltetrazolium reduction and light microscopy, was shortened significantly (P < 0.001) in cancer cells exposed to aglycones, viz., limonin, nomilin, obacunone, and deacetylnomilin. SH-SY5Y cells were more sensitive than Caco-2 cells to the limonoids, whereas noncancerous CHO cells showed hardly any change in cell numbers or cell morphology. Aglycone toxicity was dose dependent, but below the killing potential of glucosides. This observation correlated with a slower rate of induction of caspase 3/7 activity by aglycones. A flow cytometric analysis of SH-SY5Y cells treated with glucosides and aglycones showed an increased ploidy, which is consistent with enhancing chromosomal abnormalities. The results confirm that limonoids exert a strong multifaceted lethal action against cancer cells, but are relatively ineffective against CHO cells. Of the two, metabolites derived from glucosides are the more likely progenitors of an apoptosis response in situ.

Supercritical fluid extraction of limonoid glucosides from grapefruit molasses

Limonoid glucosides (primarily limonin 17-beta-D-glucopyranoside, LG) were extracted from grapefruit molasses by supercritical fluid extraction using a supercritical carbon dioxide-ethanol (SC CO(2)-ethanol) system. Extraction conditions to maximize the yield of LG were determined by varying pressure, temperature, ethanol concentration, and extraction time. The highest yield of LG at 0.61 mg/g molasses was obtained at a pressure 48.3 MPa, a temperature of 50 degrees C, 10% ethanol (X(Eth) = 0.1), and 40 min of extraction time at a flow rate of 5.0 L/min. The results demonstrated that SC CO(2) extraction of limonoid glucosides from grapefruit molasses has practical significance for commercial production.

Evaluation of the antioxidant capacity of limonin, nomilin, and limonin glucoside

The antioxidant capacity (AOC) of three representative citrus limonoids, limonin, nomilin, and limonin glucoside, was examined by the oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), beta-carotene-linoleic acid bleaching, and 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assays. Pure compounds and proper negative (cinnamic acid) and positive (2,6-di-tert-butyl-4-methylphenol (BHT) and ascorbic acid) controls were used to remove any ambiguity in interpreting results. In all cases, limonin and nomilin gave results equivalent to those of cinnamic acid, indicating that they do not possess any inherent AOC and should not be considered antioxidants. Similar results were observed for limonin glucoside, with the exception of an anomalous result obtained from the beta-carotene-linoleic acid bleaching assay. Limonin glucoside was deemed not to be an antioxidant on the basis of the three unequivocal assays.