Phenolic composition and antioxidant activity of aqueous infusions from Capparis spinosa L. and Crithmum maritimum L. before and after submission to a two-step in vitro digestion model

Changes in phytochemical composition, bioactivity and in vitro digestibility of guayusa leaves (Ilex guayusa Loes.) in different ripening stages

BACKGROUND

Guayusa (Ilex guayusa Loes.) leaves, native of the Ecuadorian Amazon, are popularly used for preparing teas. This study aimed to assess the influence of leaf age on the phenolic compounds and carotenoids and the bioactivity and digestibility (in vitro) of aqueous and hydroalcoholic leaf extracts.

RESULTS

In total, 14 phenolic compounds were identified and quantified. Chlorogenic acid and quercetin-3-O-hexose were the main representatives of the hydroxycinnamic acids and flavonols respectively. Seven carotenoids were quantified, lutein being the main compound. Ripening affected phenolic content significantly, but there was no significant difference in carotenoid content. Antioxidant capacity, measured by the DPPH^• method, was also significantly affected by leaf age. The measurement of in vitro digestibility showed a decrease in phenolic content (59%) as well as antioxidant capacity, measured by the ABTS^•+ method, in comparison with initial conditions of the guayusa infusion. Antibacterial and anti-inflammatory activities were assayed with young leaves owing to their higher phenolic contents. Guayusa did not show any antibacterial activity against Escherichia coli ATCC 25922 or Staphylococcus aureus ATCC 25923. Finally, the hydroalcoholic and aqueous extracts exhibited high in vitro anti-inflammatory activity (>65%).

CONCLUSION

Young guayusa leaves have potential applications as a functional ingredient in food and pharmaceutical industries. © 2017 Society of Chemical Industry.

Phytochemical and Pharmacological Properties of Capparis spinosa as a Medicinal Plant

Over the past decades, there has been increasing attention on polyphenol-rich foods including fruits and vegetables on human health. Polyphenols have been shown to possess some potential beneficial effects on human health and they are widely found in foods consumed by populations worldwide. Capparis spinosa (C. spinosa) is an important source of different secondary metabolites of interest to humankind. The traditional therapeutic applications of C. spinosa have been reported in Ancient Romans. Numerous bioactive phytochemical constituents have been isolated and identified from different parts (aerial parts, roots and seeds) of C. spinosa which are responsible alone or in combination for its various pharmacological activities. Therefore, this paper is a review of publications on the phytochemical and pharmacological properties of C. spinosa. There is insufficient evidence to suggest that C. spinosa or its extracts are able to improve the biomarkers of cardiovascular disease and diabetes. However, these studies used different parts of C. spinosa plant, methods of preparation and types of solvents, which cause the evaluation of activity of C. spinosa difficult and involve quite heterogeneous data. There is also evidence, although limited, to suggest benefits of C. spinosa in improving human health. Therefore, the relationship between C. spinosa and improved human health outcomes requires further study.

Effect of in vitro digestion on the functional properties of Psidium cattleianum Sabine (araçá), Butia odorata (Barb. Rodr.) Noblick (butiá) and Eugenia uniflora L. (pitanga) fruit extracts

This study evaluated the effect of in vitro digestion on the functional properties of three Brazilian native fruit extracts.

Evaluation of protective effect of different dietary fibers on polyphenolic profile stability of maqui berry (Aristotelia chilensis(Molina) Stuntz) duringin vitrogastrointestinal digestion

We investigate the protective effect of dietary fibers on the recovery and bioaccessibility indexes, and the stability of polyphenolic compounds of maqui berry powder subjected toin vitrogastrointestinal digestion.

Reversal of Doxorubicin-induced Cardiotoxicity by Using Phytotherapy: A Review

Doxorubicin as a chemotherapeutic drug is widely used for the treatment of patients with cancer. However, clinical use of this drug is hampered by its cardiotoxicity, which is manifested as electrocardiographic abnormalities, arrhythmias, irreversible degenerative cardiomyopathy and congestive heart failure. The precise mechanisms underlying the cardiotoxicity of doxorubicin are not clear, but impairment of calcium homeostasis, generation of iron complexes, production of oxygen radicals, mitochondrial dysfunction and cell membrane damage have been suggested as potential etiologic factors. Compounds that can neutralize the toxic effect of doxorubicin on cardiac cells without reducing the drug's antitumor activity are needed. In recent years, numerous studies have shown that herbal medicines and bioactive phytochemicals can serve as effective add-on therapies to reduce the cardiotoxic effects of doxorubicin. This review describes different phytochemicals and herbal products that have been shown to counterbalance doxorubicin-induced cardiotoxicity.

Searching for new sources of innovative products for the food industry within halophyte aromatic plants: In vitro antioxidant activity and phenolic and mineral contents of infusions and decoctions of Crithmum maritimum L

Aromatic halophyte plants are an outstanding source of bioactive compounds and natural products with potential use in the food industry. This work reports the in vitro antioxidant activity, toxicity, polyphenolic profile and mineral contents of infusions and decoctions from stems, leaves and flowers of Crithmum maritimum L., an aromatic and edible maritime halophyte (sea fennel). Aspalathus linearis (Burm.f.) Dahlg. (rooibos) herbal tea was used as a reference. Sea fennel's tisanes, particularly from leaves, were rich in phenolic compounds and five of them (p-hydroxybenzoic and ferulic acids, epicatechin, pyrocatechol and 4-hydroxybenzaldehyde) were here described in C. maritimum for the first time. Chlorogenic acid was the dominant phenolic determined. Na was the most abundant mineral in all tisanes followed by Ca and Mg in leaves' tisanes and K in flowers. Sea fennel's samples had a similar antioxidant activity than those from A. linearis, and had no significant toxicity towards four different mammalian cell lines. Altogether, our results suggest that sea fennel can be a source of products and/or molecules for the food industry with antioxidant properties and minerals in the form, for example, of innovative health-promoting herbal beverages.

Anti-inflammatory potential of Capparis spinosa L. in vivo in mice through inhibition of cell infiltration and cytokine gene expression

Background

Several chronic inflammatory diseases are characterized by inappropriate CD4+ T cell response. In the present study, we assessed the ability of Capparis spinosa L. (CS) preparation to orientate, in vivo, the immune response mediated by CD4+ T cells towards an anti-inflammatory response.

Methods

The in vivo study was carried out by using the contact hypersensitivity (CHS) model in Swiss mice. Then we performed a histological analysis followed by molecular study by using real time RT-PCR. We also realized a phytochemical screening and a liquid-liquid separation of CS preparation.

Results

Our study allowed us to detect a significantly reduced edema in mice treated with CS preparations relative to control. CS effect was dose dependent, statistically similar to that observed with indomethacin, independent of the plant genotype and of the period of treatment. Furthermore, our histology studies revealed that CS induced a significant decrease in immune cell infiltration, in vasodilatation and in dermis thickness in the inflammatory site. Interestingly, we showed that CS operated by inhibiting cytokine gene expression including IFNγ, IL-17 and IL-4. Besides, phytochemical screening of CS extract showed the presence of several chemical families such as saponins, flavonoids and alkaloids. One (hexane fraction) out of the three distinct prepared fractions, exhibited an anti-inflammatory effect similar to that of the raw preparation, and would likely contain the bioactive(s) molecule(s).

Conclusions

Altogether, our data indicate that CS regulates inflammation induced in vivo in mice and thus could be a source of anti-inflammatory molecules, which could be used in some T lymphocyte-dependent inflammatory diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1569-7) contains supplementary material, which is available to authorized users.

Capparis spinosa Fruit Ethanol Extracts Exert Different Effects on the Maturation of Dendritic Cells

Capparis spinosa L. (C. spinosa) has been used as food and traditional medicine and shows anti-inflammatory and anti-oxidant activities. Here, we prepared the C. spinosa fruit ethanol extracts (CSEs) using different procedures and investigated the effects of CSE on the maturation of mouse bone marrow-derived dendritic cells (DCs) in the absence or presence of lipopolysaccharide (LPS). DC maturation and cytokine production were detected by flow cytometry and ELISA, respectively. We obtained three different CSEs and dissolved in water or DMSO, named CSE2W, CSEMW, CSE3W, CSE2D, CSEMD, and CSE3D, respectively. These CSEs showed different effects on DC maturation. CSEMW and CSEMD significantly increased the expressions of CD40, CD80, and CD86, in a dose-dependent manner. CSE2W and CSE2D also showed a modest effect on DC maturation, which enhanced the expression of CD40. CSE3W and CSE3D did not change DC maturation but suppressed LPS-induced DC maturation characterized by the decreased levels of CD40 and CD80. CSE3W and CSE3D also significantly inhibited the secretions of IL-12p40, IL-6, IL-1β, and TNF-α induced by LPS. CSE3W further increased the level of IL-10 induced by LPS. Moreover, CSE3D suppressed LPS-induced DC maturation in vivo, which decreased the expressions of CD40 and CD80. These results suggested that CSE3W and CSE3D might be used to treat inflammatory diseases.

Chlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity

This review is focussed upon the acyl-quinic acids, the most studied group within theca.400 chlorogenic acids so far reported.

Metabolomic study of wild and cultivated caper (Capparis spinosa L.) from different areas of Sardinia and their comparative evaluation

Capparis spinosa L. (Capparidaceae), also known as caper, is widely known for its very aromatic flower buds (capers),that are largely employed as a flavouring in cooking. Capparis species are regarded as a potential source of important bioactive compounds, in fact, due to their botanical relationship with Brassica species; they contain glucosinolates, secondary plant metabolites, that have been studied for their potential anticarcinogenic properties. In addition, the presence of other numerous beneficial compounds such as polyphenols, alkaloids, lipids, vitamins and minerals have been reported. The aim of this study was to individuate and determinate the principal bioactive compounds occurring in different part (leaves, buds and flowers) of wild and cultivated C. spinosa collected from different area of Sardinia (Italy). Ultra-high performance liquid chromatography-triple quadrupole/linear ion trap tandem mass spectrometry methods were used for identification and simultaneous determination of 27 bioactive molecules. Analysis of different samples revealed qualitative and quantitative differences in the content of flavonoids, glucosinolates, anthocyanins and phenolic acids. In particular, glucocapparin resulted the most abundant with values ranging from 112 to 364 mg/100 g Fresh Weight (FW); followed by rutin with highest value of 126 mg/100 g FW, 4-hydroxyglucobrassicin with highest value of 42 mg/100 g FW and isorhamnetin 3-O-rutinoside with highest value of 24 mg/100 g FW. Based on this metabolomic targeted approach, quantitative results were treated by principal component analysis to explore and visualise correlation and discrimination among collections of C. spinosa samples. Copyright © 2016 John Wiley & Sons, Ltd.

Capparis Spinosa L. promotes anti-inflammatory response in vitro through the control of cytokine gene expression in human peripheral blood mononuclear cells

BACKGROUND

Capparis Spinosa L. is an aromatic plant growing wild in dry regions around the Mediterranean basin. Capparis Spinosa was shown to possess several properties such as antioxidant, antifungal, and anti-hepatotoxic actions. In this work, we aimed to evaluate immunomodulatory properties of Capparis Spinosa leaf extracts in vitro on human peripheral blood mononuclear cells (PBMCs) from healthy individuals.

RESULTS

Using MTT assay, we identified a range of Capparis Spinosa doses, which were not toxic. Unexpectedly, we found out that Capparis Spinosa aqueous fraction exhibited an increase in cell metabolic activity, even though similar doses did not affect cell proliferation as shown by CFSE. Interestingly, Capparis Spinosa aqueous fraction appeared to induce an overall anti-inflammatory response through significant inhibition of IL-17 and induction of IL-4 gene expression when PBMCs were treated with the non toxic doses of 100 and/or 500 μg/ml. Phytoscreening analysis of the used Capparis Spinosa preparations showed that these contain tannins; sterols, alkaloids; polyphenols and flavonoids. Surprisingly, quantification assays showed that our Capparis Spinosa preparation contains low amounts of polyphenols relative to Capparis Spinosa used in other studies. This Capparis Spinosa also appeared to act as a weaker scavenging free radical agent as evidenced by DPPH radical scavenging test. Finally, polyphenolic compounds including catechin, caffeic acid, syringic acid, rutin and ferulic acid were identified by HPLC, in the Capparis spinosa preparation.

CONCLUSION

Altogether, these findings suggest that our Capparis Spinosa preparation contains interesting compounds, which could be used to suppress IL-17 and to enhance IL-4 gene expression in certain inflammatory situations. Other studies are underway in order to identify the compound(s) underlying this effect.

Sea fennel (Crithmum maritimum L.): phytochemical profile, antioxidative, cholinesterase inhibitory and vasodilatory activity

Sea fennel, a rediscovered star of the coastal cuisine, has been investigated for its phytochemical profile and biological potential. Sea fennel flowers, stems and leaves were analyzed for essential oils (EOs) isolated by hydrodistillation, as well as non-volatiles obtained by ethanolic extraction. Limonene were found to be a dominant compound in EOs and ethanolic extracts; ranging from 57.5-74.2 % and 0.7-8.1 mg/g dry plant material, respectively. In addition total phenolic content was determined for ethanolic extracts. All samples and their main phytochemicals were tested for various methods. EO and extract obtained from flowers were tested for vasodilatory activity on rat aortic rings. Antioxidant activity of EOs was extremely low in comparison to extracts, on the contrary to cholinesterase inhibition where EOs showed better activity than extracts. Flower extract and chlorogenic acid showed stronger vasodilators in comparison to EO and limonene. The obtained results point out the potential impact of the dominant compounds from EO and extract on the biological properties of the sea fennel.

Pharmacological Effects of Capparis spinosa L

Medicinal plants have been known as one of the most important therapeutic agents since ancient times. During the last two decades, much attention has been paid to the health-promoting effects of edible medicinal plants, because of multiple beneficial effects and negligible adverse effects. Capparis spinosa L. is one of the most common medicinal plants, used widely in different parts of the world to treat numerous human diseases. This paper aims to critically review the available scientific literature regarding the health-promoting effects of C. spinosa, its traditional uses, cultivation protocols and phytochemical constituents. Recently, a wide range of evidence has shown that this plant possesses different biological effects, including antioxidant, anticancer and antibacterial effects. Phytochemical analysis shows that C. spinosa has high quantities of bioactive constituents, including polyphenolic compounds, which are responsible for its health-promoting effects, although many of these substances are present in low concentrations and significant changes in their content occur during processing. In addition, there is negligible scientific evidence regarding any adverse effects. Different health promotion activities, as well as tremendous diversity of active constituents, make C. spinosa a good candidate for discovering new drugs. However these findings are still in its infancy and future experimental and clinical studies are needed. Copyright © 2016 John Wiley & Sons, Ltd.

Encapsulation of Beetroot Pomace Extract: RSM Optimization, Storage and Gastrointestinal Stability

One of the great problems in food production are surplus by-products, usually utilized for feeding animals and for preparation of dietary fibre or biofuel. These products represent potential sources of bioactive antioxidants and colour-giving compounds which could be used in the pharmaceutical industry and as food additives. In the present study beetroot pomace extract was encapsulated in soy protein by a freeze drying method. Process parameters (core: wall ratio, extract concentration and mixing time) were optimized using response surface methodology (RSM) in order to obtain the optimum encapsulate (OE) with the highest polyphenol encapsulation efficiency (EE) and radical scavenging activity on DPPH radicals (SA). Using the calculated optimum conditions, the EE (86.14%) and SA (1668.37 μmol Trolox equivalents/100 g) of OE did not differ significantly (p < 0.05) from the predicted ones. The contents of total polyphenols (326.51 mg GAE/100 g), flavonoids (10.23 mg RE/100 g), and betalains (60.52 mg betanin/100 g and 61.33 mg vulgaxanthin-I/100 g), individual content of phenolic compounds and betalains by HPLC, and the ability to reduce Fe(3+) ions, i.e., reducing power (394.95 μmol Trolox equivalents/100 g) of OE were determined as well. During three months of storage at room temperature, polyphenol retention was much higher (76.67%) than for betalain pigments, betacyanins (17.77%) and betaxanthins (17.72%). In vitro digestion and release of phenolics from OE showed higher release rate in simulated intestinal fluid than in gastric fluid. These results suggest encapsulation as a contemporary method for valorisation of sensitive bioactive compounds from food industry by-products.

Effect of in vitro gastrointestinal digestion on the bioavailability of phenolic components and the antioxidant potentials of some Turkish fruit wines

This study was designed to evaluate the effects of in vitro gastrointestinal simulation method on the antioxidant potentials and phenolic profile of some Turkish fruit wines and to compare the results with a Turkish red wine prepared from native grape varieties (Papazkarası). For this purpose, blueberry, black mulberry and cherry wines were studied since they are widely consumed in Turkey. Papazkarası wine was chosen due to the lack of studies regarding this type of wine. Antioxidant potentials of samples were measured with four different methods: DPPH radical-scavenging activity, H₂O₂-scavenging activity, cupric reducing capacity and total antioxidant capacity assays. The phenolic profiles of samples were evaluated by the determination of total phenolic content and HPLC-DAD analysis of seven different molecules. The results of this study provided information not only the effect of gastrointestinal digestion on parameters mentioned above, but also the bioaccessibility about the phenolic compounds found in these four different wine samples.

In vitro analysis of the role of the mitochondrial apoptosis pathway in CSBE therapy against human gastric cancer

The caper plant (Capparis spinosa L.) was a common Uyghur folk medicine, and is a member of the Capparidaceae family. In a previous study, the n-butanol extract of C. spinosa L. (CSBE) was demonstrated to exert anti-tumor activity; however, the underlying mechanism is currently not understood. The present study aimed to elucidate the mechanism underlying the CSBE-induced mitochondrial apoptotic pathway, in order to investigate the anti-tumor effects of this plant extract. CSBE-induced apoptosis of the SGC-7901 human gastric cancer cell line was observed, and alterations in the expression levels and localization of initiators, markers, and executors of the mitochondrial apoptosis pathway were analyzed. Following treatment of SGC-7901 cells with CBSE, proliferation was inhibited and apoptosis was induced; and these effects were associated with mitochondrial membrane potential disruption, cytochrome c release into the cytoplasm, and caspase-9 and caspase-3 activation. CSBE may have induced SGC-7901 cell apoptosis by upregulating the expression of B-cell lymphoma-2 (BCL-2)-associated X protein, and downregulating the expression of BCL-2. The results of the present study suggested that CSBE may induce SGC-7901 cell apoptosis via activation of the mitochondrial apoptosis pathway.

Digestibility and Bioavailability of the Active Components of Erica australis L. Aqueous Extracts and Their Therapeutic Potential as Acetylcholinesterase Inhibitors

Erica australis L. (Ericaceae) is used in traditional medicine to treat many free-radical related ailments. In the present work, the stability and biological activity of the plant aqueous extracts submitted to an in vitro digestive process were investigated. Chemical stability was monitored by HPLC-DAD and LC-MS/MS, while the bioactivities were evaluated through the inhibition of acetylcholinesterase (AChE) and DPPH radical scavenging activity. Both extracts, whose main components were flavonol glycosides, inhibited AChE, showing IC₅₀ values of 257.9 ± 6.2 µg/mL and 296.8 ± 8.8 µg/mL for the decoction and for the infusion, respectively. Significant radical scavenging activities were also revealed by both extracts, as denoted by the IC₅₀ values for the decoction, 6.7 ± 0.1 µg/mL, and for the infusion, 10.5 ± 0.3 µg/mL. After submission to gastric and pancreatic juices, no remarkable alterations in the composition or in the bioactivities were observed, suggesting that the extracts may pass through the gastrointestinal tract, keeping their composition and therefore their biological properties. Moreover, the bioavailability of the components of both extracts, as studied in a Caco-2 cell model, showed that compounds can permeate the membrane, which is a condition to exert their biological activities. Our results add further support to the potential of E. australis for its antioxidant and neuroprotective properties.

Stability of iron-quercetin complexes in synthetic wine under in vitro digestion conditions

Wine is a dietary source of polyphenolic compounds with reported health benefits when moderately consumed. Several of these compounds can associate with metals forming complexes. Therefore, this work was conducted to reach a better understanding of the nature and chemical stability of wine-derived Fe(3+)-quercetin complexes in a digestion model. The stability of the complexes in a synthetic (simulated) wine was studied before and after in vitro gastric and intestinal digestions by high-performance liquid chromatography (HPLC) with UV-Vis detection. Metal determination was performed by atomic absorption spectrometry (ETAAS) to evaluate possible dissociation of complexes. During HPLC analysis all peaks eluted from the chromatographic column were collected, acidified, and analyzed by ETAAS. The results showed that complexes remain substantially stable after gastric digestion conditions, with recoveries of 84% to 90%. Although metal complexes were partially degraded during intestinal digestion, 41% to 45% of the Fe(3+)-quercetin complexes was recovered.

PRACTICAL APPLICATION

This work reveals the chemical stability of Fe3+–quercetin complexes in synthetic wines after an in vitro gastrointestinal digestion. The knowledge of this process would be useful to understand the bioavailability of these compounds.

Antioxidant capacity of flaxseed products: the effect of in vitro digestion

This study evaluated the effect of in vitro digestion of flaxseed products on Folin-Ciocalteu reagent reducing substances (FCRRS), its antioxidant capacity and prevention of oxidative DNA damage in human monocyte cell line U937. Flaxseed protein isolate was obtained from defatted flaxseed meal and the protein hydrolysate with high antioxidant capacity was obtained from hydrolysis of the protein isolate with Alcalase in a two factor central composite rotatable design (pH 8.5 and enzyme: substrate 1:90, w/w). The FCRRS content and antioxidant capacity measured by FRAP and ORAC in aqueous and 70 % methanol extracts were the highest in protein hydrolysate, followed by protein isolate, while the defatted meal showed the lowest values. After in vitro gastrointestinal digestion, the FCRRS content of protein isolate and hydrolysate reached similar values, however the hydrolysate had the highest antioxidant capacity, measured by FRAP while the isolate had the highest ORAC values. The defatted meal showed the lowest capacity in all assays (p < 0.05). The hydrolysate did not protect against DNA damage induced by H2O2 in U937 cells under the conditions of the present study. The results suggest that flaxseed protein isolate and hydrolysate are potential functional food ingredients with antioxidant capacity.

The type and concentration of milk increase the in vitro bioaccessibility of coffee chlorogenic acids

Coffee with different types and concentrations of milk was digested with pepsin (2 h) and pancreatin (2 h) to simulate gastropancreatic digestion. Chlorogenic acids (CGAs) were determined by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry in ultrafiltrate (cutoff 3 kDa) to evaluate their bioaccessibility. After digestion, bioaccessible CGAs decreased from 80.2 to 53.0 and 69.5 μmol/200 mL in coffee without milk and coffee-whole milk, respectively. When whole, semiskimmed, skimmed, or diluted milk were present, the increase in bioaccessibility was dependent on fat content (r = 0.99, p < 0.001). No relationship was observed between bioaccessibility and proteins, carbohydrates, and calcium content. The addition of milk to coffee caused an immediate decrease in the bioaccessibility due to CGAs binding to proteins. After digestion, 86-94% of bound CGAs remained in the high molecular weight fraction. Casein bound 5-caffeoylquinic acid with high affinity (K(D) of 37.9 ± 2.3 μmol/L; n = 0.88 ± 0.06).

Effects of antioxidants on rapeseed oil oxidation in an artificial digestion model analyzed by UHPLC-ESI-MS

A normal diet contains large quantities of oxidized fatty acids, glycerolipids, cholesterol, and their cytotoxic degradation products because many foods in the diet are fried, heated, or otherwise processed and consumed often after long periods of storage. There is also evidence that the acid medium of the stomach promotes lipid peroxidation and that the gastrointestinal tract is a major site of antioxidant action, as demonstrated by various colorimetric methods. The identity and yields of specific products of lipid transformation have seldom been determined. The present study describes the molecular species profiles of all major gastrointestinal lipids formed during digestion of autoxidized rapeseed oil in an artificial digestion model in the presence of L-ascorbic acid, 6-palmitoyl-O-L-ascorbic acid, 3,5-di-tert-butyl-4-hydroxytoluene (BHT), DL-α-tocopherol, and DL-α-tocopheryl acetate. Differences in oxidized lipid profiles were detected in the samples digested in the presence of different antioxidants, but none of them could prevent the formation of oxidized lipids or promote their degradation in a gastric digestion model. The lack of effect is attributed to the inappropriate nature of the gastrointestinal medium for the antioxidant activity of these vitamins and BHT. A fast ultrahigh performance liquid chromatographic-electrospray ionization-mass spectrometric method was developed for the analysis of lipolysis products, including epoxy, hydroperoxy, and hydroxy fatty acids, and acylglycerols, utilizing lithium as ionization enhancer.