Phenolic Acids – Occurrence and Significance in the World of Higher Fungi
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29-a volumo MIR N-ro 2 (115) Decembro 2020 Phenolic acids – Occurrence and Significance in the World of Higher Fungi BALIK Monika1, SUŁKOWSKA– ZIAJA Katarzyna2*, ZIAJA Marek3, MUSZYŃSKA Bożena2 1Jagiellonian University Medical College, Faculty of Pharmacy, Chair and Department of Pharmaceu- tical Botany – Students’ Science Society, Medyczna 9, 30–688, Kraków, Poland 2Jagiellonian University Medical College, Faculty of Pharmacy, Chair and Department of Pharmaceu- tical Botany, Medyczna 9, 30–688, Kraków, Poland 3Jagiellonian University Medical College, Faculty of Medicine, Department of Histology, Kopernika 7, 31–034 Kraków, Poland Abstract Phenolic acids constitute a chemically diverse group of bioactive compounds. The activity of phenolic acids is related to the presence of hydroxycarboxylic groups and their position on the aromatic ring. These are compounds commonly found in nature – they are present in many spe- cies of plants and fungi. In the world of higher fungi, they constitute the most numerous group among phenolic compounds. The most common phenolic acids in the world of fungi are caffeic acid, gallic acid, gentisic acid, ferulic acid, p–coumaric acid, p–hydroxybenzoic acid, protocate- chuic acid, vanillic acid, and a compound with a structure similar to phe- nolic acids – t–cinnamic acid. Phenolic acids found in fruiting bodies of mushrooms show, among others, antioxidant, antimicrobial, and anti- cancer properties. Keywords: phenolic acids, higher fungi, biological activity *Corresponding Author: Katarzyna Sułkowska-Ziaja; [email protected] 72 29-a volumo MIR N-ro 2 (115) Decembro 2020 Definition, biosynthesis and chemical genic acid). Besides, complexes of phenolic acids structure with sterols and fa"y acids have been identified [1-3] Phenolic acids (phenolcarboxylic acids) Based on numerous analyses, proved that are substances containing an aromatic ring phenolic acids are the dominant quantitative substituted by at least one hydroxyl and a car- group of phenolic derivatives found in higher boxyl group. Depending on the number of fungi [4,5]. In the studies carried out by Barros et carbon atoms in the side chain, they can be di- al., 16 species of edible mushrooms were analy- vided into hydroxybenzoic acids and hyd zed. Apart from phenolic acids, no flavonoids roxycinnamic acids [1]. The structures of the and other phenolic derivatives were found [3]. selected phenolic acids are shown in Table 1. Similar results were obtained in the course of stu- The precursors of most phenolic acids are aro- dies conducted by researchers at the University matic amino acids – tyrosine and phenylala- of Helsinki – apart from phenolic acids, the pre- nine, which are formed by the transformation sence of flavonoids or lignans was not observed of erythrose phosphate and phosphoenolpy- in the tested mushrooms [6]. ruvic acid through the shikimic acid pathway. The most common phenolic acids in fruiting From phenylalanine and tyrosine, as a result bodies of higher fungi are p–hydroxybenzoic of their deamination, are formed cinnamic acid, gallic acid, protocatechuic acid, p–couma- acid or p–coumaric acid and its hydroxyl de- ric acid, vanillic acid, ferulic acid, gentisic acid, rivatives. Other phenolic acids can be pro- caffeic acid, and a compound with a structure ducts of the transformation of malonic or similar to phenolic acids – t–cinnamic acid. Less chorismic acid and also polyketide way [2]. frequent in fruiting bodies are syringic acid, chlo- rogenic acid, ellagic acid and veratric acid. Pro- Occurrence in the world of fungi tocatechuic acid and gallic acid are the most abundant in the arboreal species of Basidiomy- Phenolic acids are found in nature in both cota [5,7-9]. The occurrence of phenolic acids and free forms and the form of glycosides and cinnamic acid in selected higher fungi is presed esters (depsides and depsidones). In the frui- in Table 2. ting bodies of higher fungi belonging to Basi- In the fruiting bodies analyzed by Barros et diomycota, free phenolic acids are usually al. phenolic acids content ranged from 2.3 mg/100 present in small amounts. Their content de- g of dry weight (d.w) in Lactarius deliciosus to 35.7 pends on the species and degree of ripeness mg/100 g d.w in Ramaria botrytis. p–Hydroxy- of the fruiting bodies. It has been shown, that benzoic acid dominated in 50% of the analyzed at high temperatures, as well as after acid hy- species and its highest content was observed in drolysis, ester bonds are broken, and free phe- Agaricus silvicola (23.9 mg/100 g d.w.). Protocate- nolic acids are released [1]. chuic and vanillic acids were identified in two Hydroxybenzoic acid derivatives most species studied, while p–coumaric acid was iden- often occur in a bonded form as components tified in three species. In Cantharellus cibarius, Ly- of complex structures such as lignin and hy- coperdon perlatum, Macrolepiota procera confirmed drolysable tannins. They also form complexes the presence of t–cinnamic acid (1.5; 1.4; 2.2 with simple sugars or ester complexes with mg/100 g d.w.) respectively [3,10]. The presence organic acids. Hydroxycinnamic acid deriva- of p–hydroxybenzoic acid has also been confir- tives also occur in a bound form. Most often med in other species of i.a. Tricholoma equestre they form complexes with compounds such and Amanita rubescens [11]. Noechlorogenic acid as chitin or proteins, while with organic, tar- (3-O-caffeoylquinic acid) is the dominant pheno- taric, or quinic acids they form ester connec- lic acid in Cantharellus cibarius fruiting bodies, tions (e.g. 5–O–caffeoylquinic acid – chloro- while 4–O–caffeoylquinic, chlorogenic, caffeic 73 29-a volumo MIR N-ro 2 (115) Decembro 2020 and p–coumaric acids are present in much while protocatechuic acid (9.6 mg/100 g d.w.), smaller quantities. The total phenolic acid caffeic acid (1.8 mg/100 g d.w.) and p–coumaric content of Cantharellus cibarius is approxima- acid (3.8 mg/100 g d.w.) were found in Sparassis tely 2.0 mg/100 g d.w [8]. crispa [13]. One of the phenolic acid–richest species The content of phenolic acids determined in is Fistulina hepatica, in which the content of edible mushrooms by Vaz et al., ranged from ap- these compounds was about 55.1 mg/100 g proximately 0.4 mg/100 g d.w. in Armillaria mel- d.w., of which about 50% is elagic acid, 24% lea to 8.1 mg/100 g d.w. in Coprinus comatus. In all caffeic acid, 26% p–coumaric acid [7]. the studied mushrooms, p–hydroxybenzoic acid In the studies conducted by Pu"araju et (0.4 to 6.2 mg/100 g d.w.) was present, which was al., the chemical composition and antioxidant quantitatively dominant. The presence of p–cou- activity of 23 species of edible fungi were ana- maric acid (0.2 to 1.9 mg/100 g d.w. ) and proto- lyzed. The dominant phenolic acids in the ex- catechuic acid has also been confirmed. [14] tracts obtained from fruiting bodies were Analysis of the six selected species of the gallic, protocatechuic and gentisin acids, the genus Cortinarius showed that the richest in phe- presence of which has been confirmed in nolic acids was Cortinarius speciosissimus. In this most species. t–Cinnamic, syringic, caffeic, fe- species determined p–hydroxybenzoic, p–cou- rulic, and p–coumaric acid were identified in maric, protocatechuic, and vanillic acids. The low or trace amounts. Besides, studies have compound identified in all the analyzed species proven a higher content of phenolic acids in was p–hydroxybenzoic acid [15]. aqueous extracts compared to methanolic ex- The analysis of the content of phenolic acids tracts [12]. in fruiting bodies is an important direction of In Agaricus bisporus, Lentinus edodes, Pleu- mycochemical research conducted in the Depar- rotus ostreatus, four phenolic acids were iden- tment of Pharmaceutical Botany at Jagiellonian tified in relatively low amounts (from 0.1 University Medical College in Kraków. The ob- mg/100 g d.w. to 0.8 mg/100 g d.w.). Quanti- jects of the studies are edible species, both wild– tatively dominant acid was p–hydroxyben- growing and from crops. The second group is zoic acid, in a low amount, was determined inedible species classified as arboreal mushro- t–cinnamic and protocatechuic acids and caf- oms. Qualitative and quantitative analyses con- feic acid [6]. firmed the presence of a wide range of hydroxy- Kim et al. carried out quantitative deter- benzoic acid and hydroxycinnamic acid deriva- mination of phenolic acids in five species of tives. In methanolic extracts obtained from edible edible fungi Pleurotus ostreatus, Agaricus bis- mushrooms such as Agaricus bisporus, Armillaria porus, Flammulina velutipes, Pleurotus eryngii, mellea, Auricularia auricula–judae, Boletus edulis, Lentinus edodes, as well as five species of fungi Cantharellus cibarius, Imleria badia, Lactarius deli- of medicinal use: Agaricus blazei, Sparassis ciosus, Leccinum scabrum, Pleurotus ostreatus, Suil- crispa, Phellinus linteus, Ganoderma lucidum, lus bovinus, Suillus luteus, Tricholoma equestre, the Inonotus obliquus. The phenolic acids content presence of protocatechuic acid, p–hydroxyben- was shown to be higher in the species of me- zoic acid, syringic acid, and gallic acid has been dicinal mushrooms. Protocatechuic acid was confirmed [16]. present in all studied species. In addition, the The presence of p–hydroxybenzoic, protoca- chemical analysis showed the presence genti- techuic, and vanillic acids was confirmed in the sin acid, p–hydroxybenzoic acid, vanillic acid, extracts of the arboreal species (Fomitopsis pini- syringic acid, t–cinnamic acid, p– and o– p– cola, Geophyllum sepiarium, Laetiporus sulphureus, coumaric acid and veratric acid. The highest Dedalepsis confragosa). The content of the indivi- content of p–hydroxybenzoic acid (26.3 dual compounds varied and ranged from 1.1 to mg/100 g d.w.) was found in Inonotus obliquus, 9.1 mg/100 g d.w.