Advances On Chemical Components And Biological Activities Of Coffee

Abstract: Coffee, one of the three top drinks in the world, belongs to Coffea (Rubiaceae), which can reduce blood sugar, and protect the liver and neuro. The chemical constituents of coffee are rich, including alkaloids, phenolic acid,flavonoids, terpene, etc. The chemical constituents are the basis of biological activities and form the characteristic flavor of the coffee. The main chemical constituents and biological activities of coffee were comprehensively reviewed, which would provide the relevant basis and theoretical support for the further development of the coffee industry. 

Key words: Coffee; Chemical constituents; Biological activities; Review

Coffee is a plant of the Rubiaceae (Coffea) genus, native to central and northern Africa, mainly distributed in a few countries such as South America, Central America, Africa and Asia. There are 66 species of coffee in 4 groups, usually referred to as the large-grained species (C. liberica), medium-grained species (C. robusta), small-grained species (C. arabica) and ethelza of the real coffee group (Eucoffea). Species (C. excelsa), of which small coffee has a mellow smell and good quality [1].

In 1892, French missionaries introduced coffee into Binchuan County, Yunnan Province for cultivation, and it has continued to expand. At present, China's coffee is mainly grown in Yunnan and Hainan, and more than 99% are distributed in Yunnan [2], with Dehong, Pu'er, Baoshan, Xishuangbanna and Lincang are the main ones, and Yunnan small-grain coffee has been evaluated as the world's high-quality coffee by the tasting experts of the International Coffee Organization. In addition, according to the records of "Chinese Materia Medica", coffee is slightly bitter, astringent, and flat;

For lack of desire, it is often used as a refreshing, diuretic and stomachic medicine. According to research reports, the chemical components contained in coffee mainly include alkaloids, phenolic acids, flavonoids, terpenes, sterol lipids and volatile components, etc., which have the functions of insulin sensitization, improving glucose metabolism, anti-diabetic and liver protection. and other pharmacological activities. This paper reviews the sources of chemical components in coffee and their biological activities, aiming to provide theoretical support for the further development of the coffee industry.

Cistanche Coffee rich in alkaloid component

1 The main ingredients of coffee

1.1 Alkaloids

Caffeine (1,3,7-trimethylxanthine, caffeine) is the main alkaloid component in coffee berries and the source of coffee bitterness. It is widely present in tea, cocoa and coffee, and is a widely used psychotropic drug one. Studies have shown that caffeine can alleviate amnesia induced by memory loss in the elderly, and can also reduce the risk of neurodegenerative diseases such as Alzheimer's disease (AD) [3], Parkinson's disease (PD) [4]. The study of Arendash et al. [5] showed that moderate intake of caffeine can inhibit memory impairment in rats; Zeitlin et al. [6] confirmed that caffeine may play a role in AD by promoting the survival of striatal and cortical cells in the brain and inhibiting the apoptosis pathway. Nakaso et al[7] confirmed that caffeine can reduce the activity of caspase-3 of cysteine and reduce nuclear fragmentation through the PD model of human bone marrow neuroblastoma cell line (SH-SY5Y). and the number of apoptotic aggregates. Caffeine can also reduce the leakage of the blood-brain barrier (BBB) caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and inhibit BBB dysfunction [8]. Regular doses of caffeine help improve hemiparesis stroke. Sun et al [9] reported that caffeine achieved protective effects on stroke through its antioxidant and anti-inflammatory properties. Caffeine has also been associated with the control of diabetes [10]. Trigonelline is a pyridine derivative that promotes the formation of aromatic compounds during coffee roasting, such as N-methylpyridine (NMP), which is a thermal degradation product of trigonelline during coffee roasting [11].

Cistanche Coffee prevents Alzheimer's disease

In recent years, more and more studies on trigonelline have been conducted, and its biological value has become more and more prominent. Liu et al. [12] reported that trigonelline can reduce blood sugar, increase the expression of insulin β cells, and regulate inflammatory responses; by down-regulating the expression of caspase 3, inhibiting partial apoptosis of β cells and increasing the activity of antioxidant enzymes, thereby reducing type 1 diabetes in mice. Ginsenoside Rb1 and trigonelline can prevent the development of diabetic kidney injury by regulating the expression of mir-3550 and acting on the Wnt/β-catenin signaling pathway [13]. Trigonelline has a potential therapeutic effect on the cardiac tissue of colitis [14]. Trigonelline has neuroprotective effects and is a good drug for the treatment of neurodegenerative diseases [15]. Fahanik-Babaei et al. [16] reported that trigonelline can improve cognition and alleviate nerve loss; it can prevent hepatic lipid accumulation and lipotoxicity caused by high cholesterol and high-fat diet by restoring hepatic autophagy[16]. 17]; inhibits gut microbial metabolism of choline and its associated cardiovascular risk [18].

In addition, coffee also contains theobromine (theobromine), theophylline (theophyline) and nicotinic acid (nicotinic acid). Joseph et al. [19] reported that there are 1,3,7,9-tetramethyluric acid (theacrine), liberine, and methyllibetine in coffee leaves (Table 1).

1.2 Phenolic acids and their derivatives

At present, p-hydroxybenzoic acid (phydroxybenzoic acid), vanillic acid (vanillic acid), p-coumaric acid (p-coumaric acid), ferulic acid (ferulic acid), chlorogenic acid (chlorogenic acid) have been isolated from coffee ), caffeic acid, caffeoylquinic acid, dicaffeoylquinic acid, 3-O-feruloylquinic acid, 3-O -Feruloyl-4-O-caffeoylquinic acid (3-Oferuloyl-4-O-caffeoylquinic acid), 3-O-caffeoyl-4-O feruloylquinic acid (3-O-caffeoyl-4- O-feruloylquinic acid) and other phenolic acids and caffeic acid derivatives (Table 2).

Chlorogenic acid (CGA) is the main phenolic acid compound with biological functions such as hypolipidemic, antioxidant, and antibacterial. Nishi et al. [22] reported that chlorogenic acid could significantly reduce cholesterol, triglycerides, low-density lipoprotein, and increase high-density lipoprotein; Xu et al. [23] confirmed the activity of chlorogenic acid and DNA protection. Shi[24] reported that chlorogenic acid could reverse corticosterone (CORT)-induced autophagy and apoptosis in PC12 cells, and could also regulate the AKT/mTOR pathway of PC12 cells; Su et al[25] reported that chlorogenic acid could inhibit aeruginosa Pseudomonas P1 cells

intracellular metabolism to exert antibacterial effect. Chlorogenic acid can effectively reduce the absorption and accumulation of Cd in the jejunum and protect the intestinal barrier [26]. The blood glucose test of human oral glucose for 2 h confirmed that chlorogenic acid and trigonelline have the effect of reducing the early glucose and insulin response [27]. At the same time, the thermal degradation of CGA in the coffee roasting process leads to the formation of bitter phenolic compounds and phenolic aromatic compounds. CGA can also participate in the formation of coffee color by incorporating the skeleton of melanin, which is the main cause of coffee pigmentation and astringency. reason.

1.3 Flavonoids

Flavonoids are a class of active ingredients that widely exist in natural plants and have various activities such as antioxidant, anticancer, anti-inflammatory and antibacterial [31–33]. Small-grain coffee contains flavonoids such as catechin, epicatechin, and quercetin (table 3).

1.4 Terpenes

Coffee contains a lot of terpenoids, mainly p-kauran and cafestol diterpenes, among which cafestol, cafestol and 16-O-methyl cafestol have the highest content. 16-O-Methylcaffeol has been used as a marker to distinguish small-grain coffee from medium-grain coffee. Gunning[38] used 600 MHz NMR and LC-MS to detect 16-O-methylcaffeol and 16-O-Methylcaffeicol. In recent years, Qiu Minghua et al. [39–42] isolated and identified four new para-kauri-type diterpenoid glycosides (mascarosides I~II, paniculoside VI and cofaryloside I), one para-marina twin flower from small-grained coffee beans. Alkane-type diterpenoid glycosides (villanovane I) and 7 p-kauri-type diterpene glycosides; 5 were isolated from raw beans and had no effect on HL60, A-549, SMMC-7721, MCF-7 and SW480 tumor cell lines. Inhibitory Pair-Shells

fir-type diterpenes (mascaroside III~V and 20-nor-cofaryloside I~II), 8 new coffee diterpene lactones (caffarolides A~H), of which caffarolides C, D and F have certain activity of activating platelet aggregation in vitro , the induction rates of 310–4 g/mL were (11.4±

5.5)%, (15.8±5.6)% and (7.8±3.3)%; 4 para-kauri-type diterpenes (caffruenol A, caffruenol B, caffruolide A and caffruolide B) were isolated from sun bean, and the Lipopolysaccharide-induced NO production in 264.7 macrophages was inhibited. Coffee also contains triterpenes. Wang et al. [43] first isolated four new dammarane-type triterpenes (caffruones A~D) from the dried fruit of Yunnan small coffee. This greatly enriched the types of terpenoids in coffee, and provided a lot of reference for the in-depth study of Yunnan small-grain coffee. At present, the research on terpenoid active components in coffee mainly focuses on cafestol and kahweol. Hiroaki et al. [44] reported that kaffiryl acetate and cafestol had inhibitory effects on human prostate cancer cells in a dose-dependent manner. Suck et al. [45] reported that kahweol inhibited breast cancer cell proliferation and induced cell death by inducing a caspase 3-dependent pathway. Lima et al. [46] studied the effect of cafestol on NB4, K562, HL60 and KG1 leukemia cell lines, and the results showed that cafestol has an effect on leukemia cell lines.

HL60 and KG1 cells were the most cytotoxic, reducing the proliferation of HL60 cells by 100%. Ferdrik et al [47] showed that when the concentration of cafestol was 10–8 and 10–6 mol/L, it could increase insulin secretion by 12% and 16%, respectively, and by long-term exposure, it could increase by 34% and 68%, and At 10–8 mol/L, the uptake of glucose by human skeletal muscle cells can be significantly increased by 8%. Seo et al. [48] reported that kahweol can reduce the production of interleukins 1α, 1β, 6 and tumor necrosis factor α induced by lipopolysaccharide, and can inhibit lipopolysaccharide-induced liver inflammation.

1.5 Flavor substances

In the 1960s, people began to study coffee bean flavor compounds, and in the 1970s, the correlation between flavor precursors in green coffee beans and aroma components in roasted coffee was reported [53]. Cell wall polysaccharides, lipids, proteins, sucrose, chlorogenic acid, caffeine and trigonelline are the main storage compounds of mature coffee seeds, and these substances form coffee aroma mainly through Maillard reaction, Strecker degradation, and caramelization reaction during the roasting process . There are mainly 28 kinds of characteristic flavor substances in coffee [54], (1) aldehydes and ketones are related to caramel taste/sweetness: isobutyraldehyde, 2-methylbutyraldehyde, isovaleraldehyde, 2,3-butyraldehyde diketone, 2,3-pentanedione, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 5-ethyl-4-hydroxy-2-methyl-3(2H)- Furanones and vanillins; (2) Sulfur-containing compounds associated with sulfur/roasting odors: 2-furfurylthiol, 2-methyl-3-furanthiol, 3-methylthiopropanal, 3-thiol -Butyl 3-methyl-1-carboxylate, 3-methyl-2-butene-1-thiol, methyl mercaptan, and dimethyl trisulfide compounds; (3) Pyrazine compounds are associated with earthy odors: 2 -Ethyl-3,5-dimethylpyrazine, 2-vinyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 2-vinyl-3- Ethyl-5-methylpyrazine and 2-methoxy-3-isobutylpyrazine; (4) Phenols, aldehydes related to smoke/phenolic aromas: guaiacol, 4-ethyl guaiacol, 4-vinylguaiacol, acetaldehyde, propionaldehyde, and (F)-beta-damascenone; (5) furanones associated with pungency: 3-hydroxy-4,5- Dimethyl-2(5H)-furanone and 3-hydroxy-4-methyl-5-ethyl-2(5H)-furanone. List

Yi et al[55] identified aldehydes, furans, phenols, thiazoles, alkenes, alkanes, esters, ketones, pyrroles, thiophenes, carboxylic acids from the steam distillation part of coffee oil. , 12 types of volatile components mainly composed of pyrazine. [56] identified 77 volatile components including alcohols, phenols, ethers, aldehydes, ketones, acids, esters, hydrocarbons and nitrogen oxides from Lao coffee. Hafsah et al. [57] used gas chromatography-mass spectrometry (GC-MS) to identify 101 volatile compounds from medium-grain coffee flowers, and a total of 72 volatile compounds were identified from coffee beans.

1.6 Other ingredients

In addition, coffee also contains anthrone compounds mangiferin (mangiferin) and isomangiferin (isomangiferin), coumarin compounds scopoletin (scopoletin), and carotenoids and lutein compounds [28]. Small coffee beans also contain serotonin compounds scorodocarpines D~F [58]. Coffee seeds contain β-sitosterol, stigmasterol, campesterol, cholesterol, 5-avenasterol, 7-avenasterol (7-avenasterol), 7-stigmastenol (7-stigmastenol) and other sterol components [59]; lipids mainly include myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, peanut Sour oil, etc. [59].

2 The biological activity of coffee

Coffee contains a large number of biologically active substances, which have various biological activities such as antioxidant, lipid-lowering, blood sugar-lowering, and neuroprotection.

2.1 Antioxidant

Yashin et al. [60] conducted a comprehensive review of the antioxidant activity of coffee, including in vitro antioxidant studies and assay methods, and pointed out that the antioxidant activity and total antioxidant content of roasted coffee were comparable to those of tea, cocoa, and red wine, and Chlorogenic acid, the main antioxidant in coffee beans, was significantly reduced after roasting.

2.2 Lipid-lowering effect

Duangjai et al. [61] used 3T3-L1 adipocytes to evaluate the effect of coffee cherries of different colors (green, yellow, and red) on lipogenesis and/or lipolysis, and the results showed that green coffee cherries of different colors were in 3T3-L1 adipocytes. All have lipogenesis-inhibiting activity, and red dry coffee can reduce fat accumulation by about 47%. In addition, all coffee extract main components (malic acid, quinic acid, and chlorogenic acid) except yellow fresh coffee increased glycerol release.

At the same time, the study also confirmed that small coffee pulp can reduce cholesterol in vitro and in vivo by inhibiting intestinal cholesterol absorption by down-regulating LXR activity modulated by NPC1L and the formation of micellar complexes.

The role of alcohol [62].

2.3 Hypoglycemic

Diabetes mellitus (DM) is a chronic disease with increased blood sugar levels caused by relative or absolute deficiency of insulin. The treatment of diabetes is mainly based on drug therapy and dietary management. The caffeine, chlorogenic acid, trigonelline, and other major components in coffee all have blood sugar-lowering effects. Sake et al. [63] conducted a study on the hypoglycemic effect of small coffee and its leaf ethanol extract, and the coffee extract could significantly reduce the blood sugar content of mice. Cafetol has potential antidiabetic effects, increasing glucose-stimulated insulin secretion and increasing glucose uptake by human skeletal muscle cells [64].

2.4 Neuroprotection

Epidemiological studies suggest that habitual coffee consumption may reduce the risk of Alzheimer's disease [65], and that coffee intake in male patients with primary Parkinson's disease is inversely associated with tremor severity [66]. In an APP/PS2 transgenic mouse model of Alzheimer's disease, it was confirmed that chlorogenic acid in coffee can prevent cognitive impairment. Immunohistochemical analysis showed that coffee polyphenols significantly reduced the number of plaques in the amyloid beta (Aβ) hippocampus.

2.5 Other functions

The crude extract of the pericarp of Yunnan small coffee has certain protective and recovery effects on damaged human umbilical vein endothelial cells [67]. The combined use of coffee extract and Vc can exert anti-tumor effect [68]. The methanolic extract of green coffee beans has certain anti-inflammatory activity [69]. Coffee has hepatoprotective effects, and coffee consumption reduces the risk of hepatocellular carcinoma recurrence and increases the chance of survival after orthotopic liver transplantation [70]. Coffee is inversely associated with the risk of nonalcoholic fatty liver disease [71].

3 Outlook

As one of the three major beverages in the world, coffee is closely related to our daily life. The research on the chemical composition of coffee is an important link to further develop and improve the utilization of coffee. At present, the main problems faced by my country's coffee industry are lack of brand effect and low added value. In order to solve this dilemma faced by my country's coffee industry, my country's coffee processing enterprises are actively exploring the deep processing technology of coffee, and strive to turn resource advantages into economic advantages. However, the change of this situation must be based on the in-depth study of coffee in my country.

(1) Coffee is rich in chemical components, which are the key to affecting the biological activity and flavor of coffee. Therefore, research on its chemical components will be the basis for further improving and advancing coffee research, as well as the key to improving coffee flavor.

(2) Through comprehensive and in-depth research on coffee, comprehensive utilization will be an important part of further development and utilization of coffee, such as coffee flowers, coffee leaves, coffee residues, etc. Coffee flowers contain active substances such as phenols, caffeine and trigonelline, which have antioxidant capacity and have the potential to be converted into biological sugars. Second, coffee leaves contain less caffeine and can be used as a tea substitute.

(3) The quality of Yunnan small-grain coffee is good, and its diterpenoids are unique. Therefore, it is very important to determine the relationship between its chemical components and flavor to improve coffee quality.

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