| Belonging to the genus of Russula, Russulaceae family and Russulales, commercial Russula sp. produce in Guangdong, a precious indigenous mushroom, is an edible ectomycorrhizal fungi with unique natural zest and delicious taste and with high economical value. Because of long history of using this delicious food in the distribution areas, a large scale of consuming market is formed locally. The taxonomy of Russula however has been confusing because of the variable morphology. It is very important to clarify the taxonomy of the commercial Russula sp. The biological characters of the commercial Russula sp. were studied systematically through investigation of ecological factors in the field, microscopic observation of its shapes of fruiting bodies, ectomycorrhizae, spores and, and its DNA sequences of internal transcribed spacers (ITS) and large subunit (28 S) of ribosomal RNA genes were PCR amplified, sequenced and phylogenetically analysed along with their GenBank allies. Antimicrobial activity of the different extracts of R. griseocarnosa by the disc diffusion was assayed and the main antimicrobial components of the petroleum ether and essential oil of R. griseocarnosa were analyzed by the GC-MS. Furthermore, the four methods of reducing powers, chelating effect on ferrous ions, scavenging effect on hydroxyl free radicals, and 2,2-diphenly-l-picrylhydrazyl (DPPH) radical scavenging activity were used to assay antioxidant activities of the commercial Russula sp. and antioxidant components were determined. The correlation coefficients for the correlation between antioxidant activity and flavone and total phenolic contents of R. griseocarnosa extracts were also studied.The major research results are showed as follows:1) Morphological and structural characteristics of commercial Russula sp. produce in GuangdongBased on ecological observation of commercial Russula sp. produce in Guangdong, its ecological environment was investigated in order to simulate its ecological environment when they are cultivated. Morphological and structural characteristics of the fruit body, basidiospore and ectomycorrhizae were examined using light and scanning electron microscopy. The results showed that it is a kind of ecotomycorrhizal fungi, it emerged and developed in the relatively steady ecological environment where average temperature, humidity and soil water content were 24-32℃,80-100% and 40% respectively. Among the three environmental factors, soil water content was the leadig factor. The ommercial Russula sp. grows fast after shower in the summer and autumn when it was hot. They emerged in the forest stand in which crown density was 0.9 or so. Soil pH was 3-4, and Fagaceae species dominated. The pileus was dark red in colour and context was greyish in pileus and stipe. Cystidia were highly developed. Basidiospores were 8.55-10.29×10.65-11.01μm and had large conical spines 1.14μm high and 0.57μm wide; the widest space between two adjacent ridges was 2.14μm. The trama and context are all made up of both the mycelia and vesicular tissue. It was ascertained that there was no clamp between adjacent hypha cells of the fungal mycelium irrespective of whether the stipe, or context or trama.2) Molecular identification of commercial Russula sp. produce in GuangdongIn an attempt to elucidate the identities of 8 fruitbodies of edible Russula fungi in Guangxi Pubei, Fujian Shanghang, and Guangdong Meizhou, nucleotide sequences of ITS and 28S of ribosomal RNA genes were employed for the studies of these fungi. The phylogenetic trees were generated from ITS and 28S data sets of this study along with their GenBank alies using maximum likelihood and neighbour-joining analysis methods. rDNA ITS sequences of the eight strains ranged from 681 to 699 bp in length and between 48.56%and 49.64% in GC content. The rDNA ITS sequence similarities of four strains (R1, R2, R3, R6 and R8) and Russula griseocarnosa were up to 99% except for three (R4, R5 and R7) from Fujian Shanghang, and Guangdong Meizhou, and the sequence similarities between bodies (R4, R5 and R7) and species of Russula from GenBank database couldn't identify to species level. The result demonstrated that edible Russula specimens obtained from Pubei county in Guangxi and Longwen town in Guangdong were Russula griseocarnosa, but up to two species of edible Russula occured potentially in Fujian Shanghang, and Guangdong Meizhou.Phylogenic relationships based on ITS and LSU sequences of species of Russula showed that Russula sp. from different areas were clustered together, indicated a closer consanguinity among them. Four ITS sequences (R1, R2, R6 and R7) were clustered in a group with R. griseocarnosa, and other four strains (R3, R4, R5 and R8) formed another cluster with R. emetica. LSU sequences of eight strains were located in the same branch. The phylogenic trees based on both ITS sequences and LSU sequences were shown that there were differences among all the fruitbodies of Russula sp. fom different areas.3) Analysis of nutritional components of R. griseocarnosa The general nutritional components of R. griseocarnosa were analysed according to National Standard analytic methods. The pileus and stipe of the mushroom contain 32.31% and 19.10% of crude protein,7.17% and 5.18% of crude fat,8.85% and 11.72% of crude fiber,7.84% and 6.59% of ash,2.11% and 1.97% of reducing sugars, 49.10% and 62.68% of carbohydrates respectively.Some nutritional components in R. griseocarnosa were studied by the means of amino acid analyer, atomic absorption spectrometer, HPLC, and GC/MS. The results revealed that and it can be regarded as good source of useful elements, such as P, K, Ca, Zn, Fe, Na, Mg. The content of potassium was especially high in comparison to sodium and K/Na ratio is 14.78 and 31.7 in pileus and stipe, respectively. There are seven kinds of fatty acid in pileus and stipe. Fatty acid compositions are mainly oleic acid, linoleic acid and palmitic. The content of oleic acid in pileus is high, which is 47.92% of the total fatty acid. Whereas the content of linoleic acid in stipe is high, which is 50.22% of the total fatty acid. The analysis of amino acids in R. griseocarnosa was made with reversed-phase high performance liquid chromatography. The result showed that seventeen kinds of amino acid (included seven kinds of essential amino acids) existed in R. griseocarnosa, except that tryptophane destroyed by hydrolysis is not checked out. The total content of amino acids in pileus and stipe is 12.75% and 8.98%, respectively. The percentage of essential amino acids was 46.04% and 52.18% in pileus and stipe, respectively.4) Antimicrobial activity of R. griseocarnosaAn experiment study on antimicrobial activity of the different extracts of R. griseocarnosa by the disc diffusion were reported and the main antimicrobial components of the petroleum ether and essential oil of R. griseocarnosa were analyzed by the GC-MS. The result showed the essential oil of R. griseocarnosa displayed significant antimicrobial activity to Escherichia coli, Bacillus subtilis, Staphalococeus aureus, Micrococcus luteus, salmonella sp. The petroleum ether of R. griseocarnosa inhibited Staphalococeus aureus and Micrococcus luteus. The ethanol extract of R. griseocarnosa almost did not show antimicrobial activity. The GC-MS analysis showed that the major antimicrobial components of essential oil were ketones, alkanes, aldehydes and alkenes, and petroleum ether extract were acid, ester, alkenes and alcohol.5) Determination of antioxidant activityThe total phenolic contents and flavonoid contents of the extracts were evaluated and the antioxidant activities of the extracts were assayed with antioxidant capacity in reducing powers, chelating effect on ferrous ions, scavenging effect on hydroxyl free radicals, and 2,2-diphenly-l-picrylhydrazyl (DPPH) radical scavenging method. The results showed that the methanol extract of R. griseocarnosa possessed strong reducing power, scavenging effect on hydroxyl free radicals, chelating effect on ferrous ions and DPPH radical scavenging activity in a concentration-dependent manner. There was a correlation coefficient for the correlation between reducing power and total phenolic contents of R. griseocarnosa extracts (R2=0.7831). Besides, flavone contents were also correlated well with reducing power (R2=0.8527) and scavenging capacity of DPPH (R2=0.816). Flanovoid and total phenolic can also be used as their antioxidant components and they can scavenge the radicals, have a better reducing power.6) Detection of antioxidant componentsA method for determination of 13 phenolic composition in R. griseocarnosa by reverse phase high performance liquid chromatography (RP-HPLC) was studied. Chromatographic separation was performed by Hypersil BDS-C18 column (4.6×200 mm,5μm) using the mobile phase gradient elution of methanol-0.1% phosphate mixture at 25℃, flow rate at 1.0 mL/min and detection wavelength at 273 nm. The results showed that three phenolic components were determined among them and quercetin (95.82μg/g) was the major component in R. griseocarnosa.
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