Determination of oxygen heterocyclic components in citrus products by HPLC with UV detection

Furocoumarins potentiate UVA-induced DNA damage in skin melanocytes

Epidemiological studies have found that high citrus fruit consumption was associated with higher risk of skin cancer. Citrus fruits and some vegetables contain furocoumarins, which may interact with ultraviolet radiation to induce skin cancer. We aimed to determine the effects of two furocoumarins, including 8-methoxypsoralen (8-MOP) and 6',7'-dihydroxybergamottin (DHB), on UVA-induced DNA damage in human epidermal melanocytes, the origin of melanoma. Our hypothesis was that these dietary furocoumarins increase UVA-induced DNA damage in melanocytes, compared to cells exposed to UV alone. We incubated melanocytes with 8-MOP or DHB, followed by exposure to physiological doses of UVA radiation. We used Western blots to quantify the UVA-induced DNA damage measured by the fraction of phosphorylated histone variant H2AX (γH2AX), which is a marker of DNA damage, relative to total H2AX (γH2AX/H2AX) in the presence or absence of furocoumarins. To quantify the UVA-induced change in γH2AX/H2AX, we calculated the UVA:Control ratio as the ratio of γH2AX/H2AX in UVA-exposed cells to that in cells without UVA (control). The mean UVA:Control ratios were borderline significantly higher for cells treated with 8-MOP and significantly higher for cells treated with DHB, compared to that of untreated cells. This study suggests that furocoumarins (particularly 8-MOP and DHB) enhance UVA-induced DNA damage in melanocytes, which is a potential novel mechanism for citrus and furocoumarins to elevate the risk of skin cancer.

A new single-reference quantitative method using liquid chromatography with relative molar sensitivity based on 1H-qNMR for khellactone esters from Peucedanum japonicum root extract

Khellactone ester (KLE) quantification using the absolute calibration method is difficult owing to the unavailability of standard reagents that can guarantee purity. Herein, a new method was developed to quantify KLEs from Peucedanum japonicum root extracts using liquid chromatography (LC) without utilizing standards. This method used relative molar sensitivity (RMS) and 7-ethoxy-4-methylcoumarin as a single-reference (SR) compound instead of KLE standards. RMS is the sensitivity ratio of SR to analytes, determined using an offline combination of quantitative NMR and LC. LC was performed using a triacontylsilyl silica gel column of superficially porous particles with a ternary mobile phase. The range of the method was 2.60-509 µmol/L. The accuracy and precision were reasonable. This is the first study to apply the RMS method to both conventional LC and ultra-high-performance liquid chromatography using the same mobile phase and column. This method may aid the quality assurance of foods containing KLEs.

Determination of Oxygen Heterocyclic Compounds in Foods Using Supercritical Fluid Chromatography-Tandem Mass Spectrometry

The aim of this research was to determine oxygen heterocyclic compounds in twenty-six Citrus- and cinnamon-flavoured foods using supercritical fluid chromatography in combination with triple-quadrupole mass spectrometry (SFC-QqQ-MS). According to the authors' knowledge, this is the first report on the determination of these molecules in foods by means of the SFC-QqQ-MS technique. The analytical technique normally used for their determination in foods is liquid chromatography coupled with a photodiode array detector. However, supercritical fluid chromatography is proving to be a valid alternative approach to investigating coumarins, furocoumarins and polymethoxyflavones. According to the results presented herein, each sample analysed showed the presence of molecules of interest. Coumarin was found in all the cinnamon-flavoured samples analysed in a low concentration. The presence of oxygen heterocyclic compounds in all the Citrus-flavoured samples, according to the label, comfirmed that the foods selected for this research article were prepared with Citrus fruits. Among the samples analysed, mandarin juice was the richest in bioactive compounds, representing a good source of polymethoxyflavones in a diet.

Hidden threat lurking in extensive hand hygiene during the Covid-19 pandemic: investigation of sensitizing molecules in gel products by hyphenated chromatography techniques

During the Covid-19 pandemic, health agencies worldwide have recommended frequent handwashing and sanitizing. A variety of hand gel products were made available on the market, often with fragrances added to curtail the strong smell of alcohol. Commonly used Citrus fragrances contain volatile aroma constituents and non-volatile oxygen heterocyclic compounds (OHCs), consisting mostly of polymethoxyflavones, coumarins, and furocoumarins. The latter have long been investigated for their phototoxic properties, and their safety as cosmetic product ingredients has been debated recurrently. To this concern, twelve commercial Citrus-scented products were investigated in this study. An extraction method was optimized for thirty-seven OHC compounds, obtaining absolute mean recovery values in the 73.5-116% range with only few milliliters of solvent consumption. Analysis by ultra-high-pressure liquid chromatography with tandem mass spectrometry detection evidenced that three samples did not conform to the labeling requirements for fragrance allergens (coumarin) laid down by the European Union Regulation on Cosmetic Products. The total furocoumarin (FC) content of the samples investigated was in the 0.003-3.7ppm range, with some noteworthy exceptions. Specifically, in two samples, the total FCs were quantified as 89 and 219 ppm, thus exceeding the safe limits recommended up to a factor of 15. Finally, the consistency of the volatile fingerprint attained by gas chromatography allowed drawing conclusions on the authenticity of the Citrus fragrances labeled, and several products did not conform to the information reported on the label concerning the presence of essential oils. Besides the issue of product authenticity, analytical tools and regulatory actions for widespread testing of hand hygiene products are urgent, to protect consumers' health and safety.

Safety and efficacy of feed additives consisting of expressed sweet orange peel oil and its fractions from Citrus sinensis (L.) Osbeck for use in all animal species (FEFANA asbl)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of expressed sweet orange oil and its fractions obtained from the fruit peels of Citrus sinensis (L.) Osbeck, when used as sensory additives (flavourings) in feed and water for drinking for all animal species. The presence of perillaldehyde was identified as a source of potential concern. However, in target species fed citrus by-products as part of daily feed, the use of the expressed orange oil and its fractions was not expected to increase the exposure to perillaldehyde to a relevant extent (< 10%). For dogs, cats, ornamental fish and ornamental birds not normally exposed to citrus by-products, no conclusion can be drawn. For the other species, the FEEDAP Panel concluded that the additives under assessment are safe at the maximum proposed use levels in complete feed. The FEEDAP Panel considered that the use in water for drinking is safe provided that the total daily intake of the additive does not exceed the daily amount that is considered safe when consumed via feed. No concerns for consumer safety were identified following the use of the additives up to the maximum proposed use level in feed. The additives under assessment should be considered as irritants to skin and eyes, and as skin and respiratory sensitisers. The use of the additives under the proposed conditions of use in animal feed was not expected to pose a risk for the environment. Expressed orange oil and its fractions were recognised to flavour food. Since their function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.

The association between citrus consumption and melanoma risk in the UK Biobank

BACKGROUND

Melanoma incidence has been dramatically increasing worldwide. Psoralen, a known photocarcinogen, is naturally abundant in citrus products, leading to the hypothesis that high citrus consumption may increase melanoma risk.

OBJECTIVES

To investigate the association between total citrus consumption and melanoma risk, and the association between individual citrus products and melanoma risk, and to test for interactions between total citrus intake and established melanoma risk factors.

METHODS

Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between citrus consumption and melanoma risk among 1592 cases and 197 372 controls from the UK Biobank cohort. Citrus consumption data were collected via five rounds of 24-h recall questionnaires. International Classification of Diseases codes were used to determine melanoma outcome.

RESULTS

After adjusting for potential confounders, participants in the highest category of total citrus intake (> 2 servings per day) had a significantly increased risk of melanoma (OR 1·63, 95% CI 1·24-2·12) relative to those with no consumption. For individual citrus products, participants with the most orange and orange juice consumption (> 1 serving per day) had a significantly increased melanoma risk relative to those with no consumption (OR 1·79, 95% CI 1·07-2·78 and OR 1·54, 95% CI 1·10-2·10, respectively). Fair- or very fair-skinned participants with high citrus consumption had an even greater melanoma risk (OR 1·75, 95% CI 1·31-2·29).

CONCLUSIONS

High citrus consumption was associated with an increased risk of melanoma in a large, prospective, population-based cohort. Further validation of these findings could lead to improved melanoma prevention strategies.

Ultraviolet Radiation and Basal Cell Carcinoma: An Environmental Perspective

Ultraviolet radiation (UVR) is a known carcinogen participated for the development of skin cancers. Solar UVR exposure, particularly ultraviolet B (UVB), is the mostly significant environmental risk factor for the occurrence and progress of basal cell carcinoma(BCC). Both cumulative and intermittent high-grade UVR exposure could promote the uncontrolled replication of skin cells. There are also exsiting other contributing environmental factors that combine with the UVR exposure to promote the development of BCC. DNA damage in formation of skin cancers is considered to be a result of UVR toxicity. It is UVR that could activate a series of oncogenes simultaneously inactivating tumor suppressor genes and aberrant proliferation and survival of keratinocytes that repair these damages. Furthermore, mounting evidence demonstrates that inflammatory responses of immune cells in the tumor microenvironment plays crucial role in the skin tumorigenesis as well. In this chapter, we will follow the function of UVR in the onset and development of BCC. We describe the factors that influence BCC induced by UVR, and also review the recent advances of pathogenesis of BCC induced by UVR from the genetic and inflammatory aspects.

Citrus Consumption and Risk of Non-Melanoma Skin Cancer in the UK Biobank

Background: Non-melanoma skin cancer (NMSC) incidence has been dramatically increasing worldwide. Psoralen, a known photocarcinogen, is naturally abundant in citrus products, leading to the hypothesis that high citrus consumption may increase NMSC risk.Methods: We fitted age- and multivariable-adjusted logistic regression models to evaluate the association between citrus consumption and NMSC risk among 197,372 UKBB participants. A total of 9,613 NMSC cases were identified using International Classification of Disease 10 codes. Citrus consumption data were collected via five rounds of 24-hour recall questionnaires.Results: We found no association between high total citrus consumption and NMSC risk, although a slightly elevated NMSC risk was observed among participants who consumed >0 to half a serving of total citrus per day (OR [95% CI] = 1.08 [1.01-1.16]). There was no association between individual citrus products and NMSC risk.Conclusion: High citrus consumption was not associated with an increased risk of NMSC in our UKBB sample. Further studies are needed to clarify these associations.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1952439 .

Dietary Intake of Coumarins and Furocoumarins through Citrus Beverages: A Detailed Estimation by a HPLC-MS/MS Method Combined with the Linear Retention Index System

Official regulations concerning the maximum number of substances in food are introduced as a consequence of possible adverse effects, after oral administration. In this regard, analytical methods are necessary in order to determine specific targets. Among oxygen heterocyclic compounds (OHCs, that are furocoumarins, coumarins and polymethoxyflavones), only coumarin is subject to restriction by the Regulation (EC) No 1334/2008 of the European Parliament. Furocoumarins are known for their phototoxicity and other side effects due to their dietary intake; however, an official limit about the maximum content of these compounds in food is still missing. The lack of information about the real amount of these compounds in food is responsible for the conflicting opinions about the introduction of an official limit. The HPLC-MS/MS method here proposed, in combination with the linear retention index system, represents an innovative analytical strategy for the characterization of OHCs in citrus beverages. Several types of drinks were analysed in order to quantify 35 OHCs in total. This method is suitable for the quality control of OHCs in food and the obtained results may be considered as informative data useful for the regulatory authorities in the emission of new opinions and for a potential new regulation in this field.

Linear retention index approach applied to liquid chromatography coupled to triple quadrupole mass spectrometry to determine oxygen heterocyclic compounds at trace level in finished cosmetics

In the European Union, cosmetic products are regulated by the Cosmetics Regulation (EC) No. 1223/2009. The Analytical Working Group of the International Fragrance Association (IFRA) suggested that a new sensitive analytical method is needed to determine psoralens in finished cosmetic products. This research provides an HPLC-MS/MS method for the quality control of 20 furocoumarins, 8 coumarins and 7 polymethoxyflavones in cosmetics. Thanks to the high sensitivity of the tandem mass spectrometry detection in Multiple Reaction Monitoring mode, psoralens contained in trace have been quantified in different products. The Limits of Quantifications were in the range 0.3-74 μg L^-1. A reliable identification was achieved combining the Linear Retention Index (LRI) system with the MS and MS/MS libraries. In particular, the attribution was based on the spectra similarity filtered by the LRI parameter. The robustness and reproducibility of the LRI approach was demonstrated by the comparison of the HPLC-MS/MS results here reported with those obtained in our previous study, by using an HPLC-PDA system. This method could be taken into account for quality control of furocoumarins in cosmetics, and by the main associations, such as IFRA, for the purpose of issuing new opinions.

Citrus Consumption and the Risk of Non-Melanoma Skin Cancer in the Women's Health Initiative

Simple Summary

Citrus products are rich in furocoumarins, which can increase the risk of incident non-melanoma skin cancer (NMSC) when combined with ultraviolet radiation. However, few observational studies have evaluated the link between citrus intake and NMSC incidence. The aim of this study was to determine whether citrus intake was related to the NMSC incidence in participants of the Women’s Health Initiative Observational Study. The results of this study indicated that high citrus juice consumption was associated with a higher risk of incident NMSC compared to low consumption. These findings add further evidence of the potentially carcinogenic nature of certain citrus products and highlight the need to continue investigations in identifying risk factors and mechanisms.

Abstract

Evidence from animal studies suggests that furocoumarins, compounds present in citrus products, can increase the risk of non-melanoma skin cancer (NMSC) when combined with ultraviolet radiation. The objective of this study was to determine the relationship between citrus intake and NMSC risk among postmenopausal women from the Women’s Health Initiative (WHI) Observational Study, who were aged 50–79 years at enrollment (1993–1998). The consumption of citrus fruit, citrus juice, and non-citrus fruit and juice were measured at the baseline of the study using a food frequency questionnaire (FFQ). NMSC cases (basal or squamous cell carcinomas) were self-reported during annual follow-up surveys. The outcome data used for this analysis were collected through March 2020. The relative risk (RR) for incident NMSC by citrus consumption was calculated. Among 49,007 non-Hispanic white participants, there were 8642 cases of incident NMSC. Using less than one serving of citrus juice per week as reference, the RRs and 95% confidence intervals (CI) for incident NMSC by citrus juice intake were 1.03 (0.95, 1.10) for one serving/week, 1.06 (1.00, 1.12) for two to four servings/week, 0.98 (0.90, 1.07) for five to six servings/week, and 1.08 (1.02, 1.13) for one or more serving/day (p-trend = 0.007). Subgroup analyses did not reveal meaningful associations by sun exposure variables. In conclusion, there were indications of a slightly higher risk of incident NMSC among citrus juice consumers; however, further longitudinal and mechanistic studies are needed to confirm the key risk factors.

Coumarins, psoralens, and quantitative 1H-NMR spectroscopy for authentication of lemon (Citrus limon [L.] Burm.f.) and Persian lime (Citrus × latifolia [Yu.Tanaka] Tanaka) juices

Mutual adulterations of lemon and lime juices may be detected using coumarins and psoralens as markers. Poor manufacturing practices or legal but mechanically intense processing of lemons were recently suspected to lead to false accusations of deliberate adulterations with lime juices due to potentially unspecific markers. Therefore, we studied coumarin and psoralen profiles in carefully dissected flavedo, albedo, and endocarp of lime and lemon as well as in juices produced under variable mechanical stresses at laboratory and pilot plant scale. Although the marker herniarin was detectable in juices from lime and harshly extracted lemons at low levels, isopimpinellin, bergapten and the herein proposed, tentatively assigned 5-geranyloxy-8-methoxypsoralen represented unambiguously lime-specific markers. Coumarin and psoralen data also allowed differentiating juices produced at differing degrees of mechanical stress. The latter was also possible using quantitative ¹H-NMR spectroscopy, which yielded best results when combined with HPLC data on coumarins and psoralens. In the future, the reported approach may be used for establishing a robust database prior to being used in industrial practice.

Intake of Furocoumarins and Risk of Skin Cancer in 2 Prospective US Cohort Studies

BACKGROUND

In prior studies, higher citrus consumption was associated with higher risk of cutaneous malignant melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC). Furocoumarins, compounds with phototoxicity and photocarcinogenicity in citrus, may be responsible for the association.

OBJECTIVES

The objective of the study was to investigate the association between furocoumarin intake and skin cancer risk.

METHODS

A total of 47,453 men from the Health Professionals Follow-Up Study (HPFS) and 75,291 women from the Nurses' Health Study (NHS) with diet data collected every 2-4 y in the 2 prospective cohort studies were included. A furocoumarin food composition database for 7 common furocoumarins [bergaptol, psoralen, 8-methoxypsoralen, bergapten, 6',7'-dihydroxybergamottin (6'7'-DHB), epoxybergamottin, and bergamottin] was developed and used to calculate participants' cumulative average and energy-adjusted furocoumarin intake. Multivariate HRs and 95% CIs of the associations between furocoumarin intake and skin cancer risk were estimated using Cox proportional hazards models. Analyses were performed separately in each cohort as well as pooled using a fixed-effects model.

RESULTS

Throughout follow-up (1984-2012 in the NHS and 1986-2012 in the HPFS), we identified 1593 melanoma, 4066 SCC, and 28,630 BCC cases. Higher intake of total furocoumarins was associated with an increased risk of BCC; the pooled HR comparing the top with the bottom quintile was 1.16 (95% CI: 1.11, 1.21; P-trend = 0.002). Higher intakes of bergaptol, bergapten, 6'7'-DHB, and bergamottin were also significantly associated with increased BCC risk. No significant associations were found between intake of total furocoumarins and the risks of SCC or melanoma.

CONCLUSIONS

Intakes of total furocoumarins as well as some individual furocoumarins were associated with an increased risk of skin cancer, especially BCC, in 2 cohorts of US health professionals.

A rapid UHPLC-QqQ-MS/MS method for the simultaneous qualitation and quantitation of coumarins, furocoumarins, flavonoids, phenolic acids in pummelo fruits

The impact of secondary metabolites on fruit quality, plant growth and human health has led to an increased demand for analytical methods to characterize and quantify these metabolites in recent years. A versatile, sensitive and rapid method based on UHPLC-QqQ-MS/MS was developed for simultaneous qualitation and quantitation of coumarins, furocoumarins, flavonoids and phenolic acids. The chromatographic elution and multiple reaction monitoring mode transitions were optimized to achieve good separation and accurate quantitation of 47 analytes, including 13 groups of isomers, during a single 13 min chromatographic run. This method was validated with good precision and recoveries, wide linear ranges and low limits of detection and quantitation (0.014-1.50 μg L-1). The validated method was further applied to quantify the analytes in flavedo, albedo and pulp from two pummelo varieties, C. grandis 'Shatianyu' and C. grandis 'Guanximiyu'. This method combines high sensitivity, good selectivity, and short chromatographic run time.

Volatile Organic Compounds Profiles to Determine Authenticity of Sweet Orange Juice Using Head Space Gas Chromatography Coupled with Multivariate Analysis

An efficient and practical method for identifying mandarin juice over-blended into not from concentrate (NFC) orange juice was established. Juices were extracted from different cultivars of sweet orange and mandarin fruits. After being pasteurized, the volatile organic compounds (VOCs) in the juice samples were extracted using headspace solid-phase microextraction, and qualitatively and quantitatively analyzed using gas chromatography–mass spectrometry detection. Thirty-two VOCs contained in both the sweet orange juice and mandarin juice were used as variables, and the identification model for discriminating between the two varieties of juice was established by principal component analysis. Validation was applied by using common mandarin juices from Ponkan, Satsuma and Nanfengmiju cultivars blended at series of proportions into orange juices from Long-leaf, Olinda, and Hamlin cultivars. The model can visually identify a blending of mandarin juice at the volume fraction of 10% or above.

Evaluation of furanocoumarins from seeds of the wild parsnip (Pastinaca sativa L. s.l.)

Although the wild parsnip (Pastinaca sativa L. s.l.) fruits are known to contain linear and angular furanocoumarins, the individual components of the seeds have not been fully identified and quantitated, and, in the case of immature seeds, reported. In view of this, the main furanocoumarin compounds were extracted using pyridine, and were isolated using semi-preparative high-performance liquid chromatography. The structural elucidation of isolated compounds was done based on detailed spectral analysis conducted by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/MS), ¹H and ¹³C NMR and, where possible, by gas chromatography-mass spectrometry (GC-MS). The quantitative analysis of furanocoumarin compounds in the wild parsnip was conducted by analytical ultra-performance liquid chromatography (UPLC-DAD), calculated against the standard curves of isolated compounds. The total yields of furanocoumarin compounds from the seeds after extraction with pyridine were 107.2-222.8 mg g^-1 (fresh weight) and 50.2-66.4 mg g^-1 (soluble dry matter). Thirteen furanocoumarins were identified. The main compounds (percentage in FW) in immature seeds were bergapten (40.8), pimpinellin (10.5), methoxsalen (5.7), isopimpinellin (4.3), imperatorin (3.2), and phellopterin (7.2). Seven constituents previously not described in P. sativa seeds and its products were identified, namely, byakangelicol (14.4), heraclenin (8.5), isobergapten (2.5), byakangelicin (1.3), heraclenol (0.5), psoralen (0.3), and isobyakangelicin (0.8). The latter is a new compound of the Apiaceae family. Extraction of immature seeds using pyridine gave a much higher yield and a greater variety of furanocoumarins. This indicates that the wild parsnip, along with other Apiaceae family plants, may be an important source of bioactive compounds.

Intake of folate and other nutrients related to one-carbon metabolism and risk of cutaneous melanoma among US women and men

BACKGROUND

Nutrients involved in one-carbon metabolism - folate, vitamins B6 and B12, methionine, choline, and betaine - have been inversely associated with multiple cancer sites and may be related to skin cancer. However, there is a lack of research on the association between intake of these nutrients and cutaneous melanoma risk. The aim of this study was to examine the associations between intake of one-carbon metabolism nutrients and cutaneous melanoma risk in two large prospective cohorts.

METHODS

The cohorts included 75,311 white women and 48,523 white men. Nutrient intake was assessed repeatedly by food frequency questionnaires and self-reported supplement use. We used Cox proportional hazards regression to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) and then pooled HRs using a random-effects model.

RESULTS

Over 24-26 years of follow-up, we documented 1328 melanoma cases (648 men and 680 women). Higher intake of folate from food only, but not total folate, was associated with increased melanoma risk (pooled HR for top versus bottom quintile: 1.36; 95% CI: 1.13-1.64; P for trend = 0.001). The association was significant in men, but attenuated in women. Higher intake of vitamins B6 and B12, choline, betaine, and methionine were not associated with melanoma risk, although there was modest increasing trend of risk for vitamin B6 from food only (pooled HR for top versus bottom quintile: 1.18; 95% CI: 0.99-1.41; P for trend = 0.03).

CONCLUSIONS

We found some evidence that higher intake of folate from food only was associated with a modest increased risk of cutaneous melanoma. However, since other factors related to dietary folate intake may account for the observed association, our findings warrant further investigation.

Novel coumarin-pyrazole carboxamide derivatives as potential topoisomerase II inhibitors: Design, synthesis and antibacterial activity

The identification of novel Topoisomerase II (Topo II) inhibitors is one of the most attractive directions in the field of bactericide research and development. In our ongoing efforts to pursue the class of inhibitors, six series of 70 novel coumarin-pyrazole carboxamide derivatives were designed and synthesized. As a result of the evaluation against four destructive bacteria, including Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella. Compound 8III-k (MIC = 0.25 mg/L) showed considerable inhibitory activity than ciprofloxacin (MIC = 0.5 mg/L) against Escherichia coli and 8V-c (MIC = 0.05 mg/L) exhibited excellent antibacterial activity than ciprofloxacin (MIC = 0.25 mg/L) against Salmonella. The selected compounds (8III-k, 8V-c and 8V-k) exhibit potent inhibition against Topo II and Topo IV with IC₅₀ values (9.4-25 mg/L). Molecular docking model showed that the compounds 8V-c and 8V-k can bind well to the target by interacting with amino acid residues. It will provide some valuable information for the commercial Topo II inhibiting bactericides.

Determination of citrus juice coumarins, furanocoumarins and methoxylated flavones using solid phase extraction and HPLC with photodiode array and fluorescence detection

A synergistic combination of analytical techniques was developed for the simultaneous determination of the three most biologically active chemical families in citrus juices: methoxylated flavones, coumarins, and furanocoumarins. No rapid methodology has been available to determine them together. A solid phase extraction concentrated these groups and a ternary reverse phase HPLC gradient completely resolved them from other juice components. Two coumarins, isomeranzin and osthole, were identified in a sweet orange (C. sinensis) cultivar, Changyecheng, for the first time. Pummelo juice was characterized by coumarin and furanocoumarin epoxides such as meranzin and epoxybergamottin. No epoxides were observed in the more acidic juices. Added furanocoumarin epoxides hydrolyzed rapidly in the most acidic juices. The ratios of the UV peak areas at 320 nm to the fluorescence emission peaks as well as the ratio of fluorescence emission peaks at 450-400 nm could be used to identify chromatographic peaks.

Furocoumarin Kinetics in Plasma and Urine of Healthy Adults Following Consumption of Grapefruit (Citrus paradisi Macf.) and Grapefruit Juice

Furocoumarins are a class of organic compounds found in a variety of vegetables and fruits. Relatively little is known about the absorption and excretion of these compounds following ingestion. The objective of this study was to identify furocoumarins in grapefruit and grapefruit juice and observe their kinetics in blood and urine. The furocoumarins detected in grapefruit using UPLC-MS/MS were bergamottin, 6',7'-dihydroxybergamottin (6',7'-DHB), epoxybergamottin, and bergaptol. Bergamottin, 6',7'-DHB, bergaptol, and bergapten were detected in grapefruit juice. In this study of 6 males and 3 females, only bergamottin and 6',7'-DHB were detected in plasma, whereas in urine, four distinct furocoumarin metabolites as well as bergaptol, 6',7'-DHB, 8-methoxypsoralen (8-MOP), bergamottin, and psoralen were identified. Following grapefruit ingestion, furocoumarins were detectable in plasma as early as 15 min and in urine within 1 h. They remained in plasma for up to 3 or more hours and in urine as late as 24 h.

Chemistry and health effects of furanocoumarins in grapefruit

Furanocoumarins are a specific group of secondary metabolites that commonly present in higher plants, such as citrus plants. The major furanocoumarins found in grapefruits (Citrus paradisi) include bergamottin, epoxybergamottin, and 6′,7′-dihydroxybergamottin. During biosynthesis of these furanocoumarins, coumarins undergo biochemical modifications corresponding to a prenylation reaction catalyzed by the cytochrome P450 enzymes with the subsequent formation of furan rings. Because of undesirable interactions with several medications, many studies have developed methods for grapefruit furanocoumarin quantification that include high-performance liquid chromatography coupled with UV detector or mass spectrometry. The distribution of furanocoumarins in grapefruits is affected by several environmental conditions, such as processing techniques, storage temperature, and packing materials. In the past few years, grapefruit furanocoumarins have been demonstrated to exhibit several biological activities including antioxidative, -inflammatory, and -cancer activities as well as bone health promotion both in vitro and in vivo. Notably, furanocoumarins potently exerted antiproliferative activities against cancer cell growth through modulation of several molecular pathways, such as regulation of the signal transducer and activator of transcription 3, nuclear factor-κB, phosphatidylinositol-3-kinase/AKT, and mitogen-activated protein kinase expression. Therefore, based on this review, we suggest furanocoumarins may serve as bioactive components that contribute, at least in part, to the health benefits of grapefruit.

Oxygenated heterocyclic compounds to differentiate Citrus spp. essential oils through metabolomic strategies

This study aimed to characterise and discriminate 44 authenticated commercial samples of citrus essential oils (EO) from seven species (bergamot, lemon, bigarade, orange, mandarin, grapefruit, lime) by analysing the non-volatile oxygenated heterocyclic compounds (OHC) by UHPLC/TOF-HRMS, multivariate data analysis (PCA, PLS-DA) and metabolomic strategies; the OHC fraction includes coumarins, furocoumarins, and polymethoxylated flavonoids. Two different approaches were adopted: (i) targeted profiling based on quantifying 18 furocoumarins and coumarins, some of which are regulated by law, and (ii) targeted fingerprinting based on 140 OHCs reported in citrus essential oils, from which 38 discriminant markers were defined. This approach correctly discriminated the Citrus species; its "sensitivity" to relatively low adulteration rate (10%) was highly satisfactory. The proposed method is complementary to that of analysing the citrus EO volatile part by GC techniques.

Citrus consumption and risk of basal cell carcinoma and squamous cell carcinoma of the skin

Animal experiments have demonstrated the photocarcinogenic properties of furocoumarins, a group of naturally occurring chemicals that are rich in citrus products. We conducted a prospective study for citrus consumption and risk of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin based on data from 41530 men in the Health Professionals Follow-up Study (1986-2010) and 63759 women in the Nurses' Health Study (1984-2010) who were free of cancers at baseline. Over 24-26 years of follow-up, we documented 20840 incident BCCs and 3544 incident SCCs. Compared to those who consumed citrus products less than twice per week, the pooled multivariable-adjusted hazard ratios were 1.03 [95% confidence interval (95% CI): 0.99-1.08] for BCC and 1.14 (95% CI: 1.00-1.30) for SCC for those who consumed two to four times per week, 1.06 (95% CI: 1.01-1.11) for BCC and 1.15 (95% CI: 1.02-1.28) for SCC for five to six times per week, 1.11 (95% CI: 1.06-1.16) for BCC and 1.22 (95% CI: 1.08-1.37) for SCC for once to 1.4 times per day and 1.16 (95% CI: 1.09-1.23) for BCC and 1.21 (95% Cl: 1.06-1.38) for SCC for 1.5 times per day or more (P trend = 0.001 for BCC and 0.04 for SCC). In contrast, consumption of non-citrus fruit and juice appeared to be inversely associated with risk of BCC and SCC. Our findings support positive associations between citrus consumption and risk of cutaneous BCC and SCC in two cohorts of men and women, and call for further investigations to better understand the potential photocarcinogenesis associated with dietary intakes.

Citrus Consumption and Risk of Cutaneous Malignant Melanoma

PURPOSE

Citrus products are widely consumed foods that are rich in psoralens and furocoumarins, a group of naturally occurring chemicals with potential photocarcinogenic properties. We prospectively evaluated the risk of cutaneous malignant melanoma associated with citrus consumption.

METHODS

A total of 63,810 women in the Nurses' Health Study (1984 to 2010) and 41,622 men in the Health Professionals Follow-Up Study (1986 to 2010) were included. Dietary information was repeatedly assessed every 2 to 4 years during follow-up. Incident melanoma cases were identified through self-report and confirmed by pathologic records.

RESULTS

Over 24 to 26 years of follow-up, we documented 1,840 incident melanomas. After adjustment for other risk factors, the pooled multivariable hazard ratios for melanoma were 1.00 for overall citrus consumption < twice per week (reference), 1.10 (95% CI, 0.94 to 1.30) for two to four times per week, 1.26 (95% CI, 1.08 to 1.47) for five to six times per week, 1.27 (95% CI, 1.09 to 1.49) for once to 1.5 times per day, and 1.36 (95% CI, 1.14 to 1.63) for ≥ 1.6 times per day (Ptrend < .001). Among individual citrus products, grapefruit showed the most apparent association with risk of melanoma, which was independent of other lifestyle and dietary factors. The pooled multivariable hazard ratio for melanoma comparing the extreme consumption categories of grapefruit (≥ three times per week v never) was 1.41 (95% CI, 1.10 to 1.82; Ptrend < .001).

CONCLUSION

Citrus consumption was associated with an increased risk of malignant melanoma in two cohorts of women and men. Nevertheless, further investigation is needed to confirm our findings and explore related health implications.

Authenticity analysis of citrus essential oils by HPLC-UV-MS on oxygenated heterocyclic components

Citrus essential oils are widely applied in food industry as the backbone of citrus flavors. Unfortunately, due to relatively simple chemical composition and tremendous price differences among citrus species, adulteration has been plaguing the industry since its inception. Skilled blenders are capable of making blends that are almost indistinguishable from authentic oils through conventional gas chromatography analysis. A reversed-phase high performance liquid chromatography (HPLC) method was developed for compositional study of nonvolatile constituents in essential oils from major citrus species. The nonvolatile oxygenated heterocyclic components identified in citrus oils were proved to be more effective as markers in adulteration detection than the volatile components. Authors are hoping such an analysis procedure can be served as a routine quality control test for authenticity evaluation in citrus essential oils.

Coumarin and furanocoumarin quantitation in citrus peel via ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-MS)

Coumarins and furanocoumarins are secondary metabolites commonly found in citrus plants. These molecules are allelochemical compounds in plants that have controversial effects on humans, such as phototoxicity and the commonly described interactions with drugs, referred to as the "grapefruit juice effect". Thus, it is important to develop a reliable method to identify and quantitate the coumarins and furanocoumarins in citrus extracts. For this purpose, we herein describe an ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-MS)-based method. We first developed a rapid UPLC method (20 min) to separate the isomers of each furanocoumarin. A subsequent single ion monitoring MS detection method was performed to distinguish between the molecules, which were possibly coeluting but had different molecular weights. The method was successfully used to separate and quantitate 6 coumarins and 21 furanocoumarins in variable amounts within peel extracts (flavedo and albedo) of 6 varieties of Citrus (sweet orange, lemon, grapefruit, bergamot, pummelo, and clementine). This method combines high selectivity and sensitivity in a rapid analysis and is useful for fingerprinting Citrus species via their coumarin and furanocoumarin contents.

HPLC-PDA-MS and NMR characterization of a hydroalcoholic extract of Citrus aurantium L. var. amara peel with antiedematogenic activity

The phytochemical profile of a hydroalcoholic extract of Citrus aurantium var. amara L. peel, used as herbal medicine, was characterized by HPLC-PDA-MS. Two di-C-glycosyl flavones (vincenin II and diosmetin 6,8-di-C-glucoside), a series of flavones (luteolin 7-O-neohesperidoside, rhoifolin, and neodiosmin), and flavanone (neoeriocitrin, naringin, and neohesperidin) 7-O-neohesperidosides and two methoxyflavones (nobiletin and tangeretin), commonly present in Citrus, were identified. Furthermore, brutieridin and melitidin, two 3-hydroxy-3-methylglutaryl flavanone glycosides, were also characterized along with rhoifolin 4'-glucoside and three coumarins (8,3'-β-D-glucopyranosyloxy-2'-hydroxy-3'-methylbutyl-7-methoxycoumarin, merazin hydrate, and isomerazin). A preparative isolation procedure followed by NMR spectroscopy confirmed the proposed structures of the major flavonoids and identified the coumarins. The phenolic content was found to be 14.8 mg mL(-1), and naringin and neohesperidin were the compounds present in the highest concentration (3.6 and 2.6 mg mL(-1)). The extract of C. aurantium peel inhibited significantly (p < 0.05) both histamine- and dextran-induced edema in rats in a concentration-dependent manner (IC(50) = 119.6 and 118.3 mg kg(-1), respectively), providing evidence for the therapeutic use of C. aurantium var. amara peel.

Determination of Bioactive Compounds in the Juice of Pummelo (Citrus grandis Osbeck)

The juice of pummelo (Citrus grandis Osbeck) was analyzed to determine its composition of flavonoids, polymethoxyflavones, coumarins and psoralens. The analyses were carried out by HPLC using columns packed with small diameter Fused-Core® C18 particles to achieve high resolution in short analysis time. In addition, the profile of the native carotenoids present in the juice was determined using a C30 column. Identification of flavonoids was achieved by MS with ESI in negative mode; the MS acquisition of oxygenated heterocyclic compounds was performed in positive APCI; carotenoids were detected with a PDA detector. Nineteen native carotenoids were determined in pummelo juice for the first time. The composition of this juice is also discussed in comparison with other Citrus juices, especially grapefruit.

Assessing the biosynthetic capabilities of secretory glands in Citrus peel

Epithelial cells (ECs) lining the secretory cavities of Citrus peel have been hypothesized to be responsible for the synthesis of essential oil, but direct evidence for such a role is currently sparse. We used laser-capture microdissection and pressure catapulting to isolate ECs and parenchyma cells (as controls not synthesizing oil) from the peel of young grapefruit (Citrus × paradisi 'Duncan'), isolated RNA, and evaluated transcript patterns based on oligonucleotide microarrays. A Gene Ontology analysis of these data sets indicated an enrichment of genes involved in the biosynthesis of volatile terpenoids and nonvolatile phenylpropanoids in ECs (when compared with parenchyma cells), thus indicating a significant metabolic specialization in this cell type. The gene expression patterns in ECs were consistent with the accumulation of the major essential oil constituents (monoterpenes, prenylated coumarins, and polymethoxylated flavonoids). Morphometric analyses demonstrated that secretory cavities are formed early during fruit development, whereas the expansion of cavities, and thus oil accumulation, correlates with later stages of fruit expansion. Our studies have laid the methodological and experimental groundwork for a vastly improved knowledge of the as yet poorly understood processes controlling essential oil biosynthesis in Citrus peel.

Identification and quantification of coumarins in Peucedanum ostruthium (L.) Koch by HPLC-DAD and HPLC-DAD-MS

The rhizomes of Peucedanum ostruthium (L.) Koch (masterwort) are traditionally used in the alpine region as ingredient of liqueurs and bitters, and as a herbal drug. A sensitive and specific high-performance liquid chromatography-diode-array detection-mass spectrometry (HPLC-DAD-MS) method has been developed for the simultaneous identification and quantification of its main coumarins, oxypeucedanin hydrate, oxypeucedanin, ostruthol, imperatorin, osthole, isoimperatorin, and ostruthin. Fast HPLC separation could be achieved on an Acclaim C18 column (150 mm × 2.1 mm i.d., 3 μm) using a mobile phase gradient of acetonitrile-water modified with 0.01% acetic acid. The quantification by HPLC-DAD was performed with imperatorin as external standard and validated to demonstrate selectivity, linearity, precision, and accuracy. The content of the main coumarins was quantitated in various batches of commercial and field-collected rhizomes of Peucedanum ostruthium, as well as in beverages prepared thereof.