Anna Wiejak, WANG Yuan-zhong, ZHANG Ji, Jerzy Falandysz*

1.University of Gdańsk, Gdańsk PL 80-308, Poland 2.Institute of Medicinal Plants, Yunnan Academy of Agricultural Sciences, Kunming 650200, China

Mercury in Sclerotia ofWolfiporiaExtensa(Peck) Ginns Fungus Collected Across of the Yunnan Land

Anna Wiejak1, WANG Yuan-zhong2, ZHANG Ji2, Jerzy Falandysz1*

1.University of Gdańsk, Gdańsk PL 80-308, Poland 2.Institute of Medicinal Plants, Yunnan Academy of Agricultural Sciences, Kunming 650200, China

Dried sclerotia ofWolfiporiaextensahas a long history of medicinal uses in Asia and also is a traditional snack in Beijing that is called “fuling jiabing”.This study aimed at providing and evaluating data on total Hg contents of sclerotia collected across of the Yunnan land in China, which is generally lacking information.Sclerotia of W.extensa showed a low contamination with Hg when compared to fruiting bodies of many mushroom species.The Hg contents ranged from 0.004 1 to 0.019 mg Hg per kg dry matter with a median value of 0.011 mg·kg-1dry matter and an overall mean value of (0.011±0.004) mg·kg-1dry matter.Mercury content of sclerotia varied between the places of collection in mountainous Yunnan.Assessed intake of Hg by adult eating 50 g of the “average” Yunnan’s origin sclerotia contained in the “Fuling jiabing” snack could be between 0.000 009 2 and 0.000 55 mg per capita or between 0.000 003 4 and 0.000 016 mg per kg body mass for a typical adult of mass 60 kg, which is a low intake and Hg intakes would even be much less if taking decoctions of sclerotia.This study has revealed that sclerotia ofW.extensashowed a weak contamination with Hg and possible Hg intake eating sclerotia ofW.extensais below health limits.Also Hg intake from the decoctions ofW.extensais much below health limits and “fulingjiabing” snack made of sclerotia ofW.extensaprovides little Hg.

Bioconcentration；Heavy metal；Fungi；Wild foods

Introduction

The fungus speciesWolfiporiaextensa(Peck) Ginns that was known earlier as Poria cocos F.A.Wolf., is a wood-decaying fungus in thePolyporaceaefamily with a terrestrial growth habitat[1].This fungus develops long-lasting underground sclerotia[2].A sclerotia is a dense mass of mycelium located under the ground (Fig.S1) and is used by fungusW.extensaand certain other species to store food reserves needed in the development of fruit bodies.Sclerotia of wild-grown fungusW.extensaweighs from around 0.5 kg mass, while a record high volume recorded was up to 25 kg fresh mass (province of Guizhou in China, Fig.S2).

Sclerotia of certain mushrooms from wild (and from field culturing in case ofW.extensa) are used as food resource and as traditional medicine in certain countries.Sclerotia of King Tuber MushroomPleurotustuber-regiumis food and also used in traditional medicine in Nigeria, while available data on their minerals content are highly limited[3-4].Sclerotia ofW.extensais called “Indian bread” by Native Americans.In the Herbal Medicine and Traditional Chinese Medicine dried sclerotia “fu-ling” ofW.extensais widely used in the form of the decoctions (usually 9 to 18 g of dried powder per day, up to 45 g) and in combination with some other herbs[5-6].The “fu-ling” is also used in making a kind of traditional snack food of Beijing that is called “fulingjiabing” and ready to use traditional Chinese medicine formulations.

Data on mineral constituents content and composition of sclerotia ofW.extensaare lacking and including information on mercury.This study is aimed at investigating the occurrence and evaluate data on mercury in sclerotia ofW.extensaand assessing possible intake of this element by individuals eating “fulingjiabing” snacks or taking decoctions for which scientific data are not available.

1 Materials and Methods

1.1 Sample collection

Sclerotia ofWolfiporiaextensa(Peck) Ginns were collected from 19 geographically and distantly distributed places of the Yunnan province in China in July 2012 (Fig.1).A total of 19 sampling places were selected at an altitude above sea level between 1371 and 2061 m.The inner part of the sclerotia “fu-lin” which is white in color and free of skin “fu-lingpi” or pine roots “fu-shen” were separated for analyses.From each sclerotia 6 sub-samples of the inner part were taken (each ca.300 g) and pooled to make a bulk sample.Further the sclerotia were sliced into small pieces, dried at 105 ℃ and powdered using porcelain mortar.The bulk samples of dry powdered sclerotia (each ca.600 g) were placed into sealed new polyethylene bags and kept in dry and clean conditions in a herbal materials depository room prior to analyses.Sub-samples (each ca.100 g) were subjected to Hg determinations.

Fig.1 Localization of the sampling places of W.extensaacross of Yunnan in China

1.2 Analysis

Total Hg content of the sclerotia was determined using a direct sample thermal decomposition (heating temperature -850 ℃) coupled with gold wool trap, desorption and cold-vapour atomic absorption spectroscopy (CV-AAS; Mercury analyzer type MA-2000, Nippon Instruments Corporation, Takatsuki, Japan) determination)[7-8].The conditions used for CV-AAS were as follows: detection-dual beam AAS; determination -7 min; wavelength -253.7 nm.

Each sample of sclerotia was examined in 3～4 replicates.For the sample size of ca 100～150 mg sclerotia, the limit of detection (LOD) of Hg was 0.001 mg·kg-1dry matter (dm), the limit of quantification (LOQ) was 0.003 mg·kg-1dm, and certified limit of linearity (LOL) for instrument was between 0.000 and 15.000 ng (r=0.998 2) at “l(fā)ow mode” and between 0.000 and 180.000 ng (r=0.999 6) at “high mode”.The analytical procedure used was subjected also to analytical control and quality assurance (AC/QA) using blank samples checks with each set of six samples of sclerotia.Also one fungal certified reference material and two herbal certified reference materials were included in the AC/QA checks of Hg determinations.

The fungal certified reference material (CS-M-4) composed of dried fruit bodies of mushroom Birch Brown Scaber StalkLeccinumscabrumwith declared value of Hg content at (0.465±0.024) mg·kg-1dm and our result was (0.472±0.030) mg·kg-1dm (n=5).The herbal certified reference materials composed of dried tea leaves (INCT-TL-1) and mixture of dried Polish herbs (INCT-MPH-2) with declared values of Hg contents at (0.005 0±0.000 7) and (0.018±0.002) mg·kg-1dm, and our results were: (0.004 50±0.000 53) (n=3) and (0.018 3±0.002 0) mg·kg-1dm (n=3).

2 Results and Discussion

Sclerotia of fungusW.extensaexamined in this study contained Hg at 0.004 1 to 0.019 mg·kg-1dm, with median value of 0.011 mg·kg-1dm and an overall mean of (0.011±0.004) mg·kg-1dm (Table 1).These values can be considered low if compared to records on Hg contents of some species of mushrooms (Macromycetes) collected from the areas unpolluted with heavy metals in Europe and elsewhere[9-14].For example, the edible fruit bodies of the Amanita mushroom, the Tawny Grisette Amanita fulva, collected from many background areas in Europe contained Hg in caps at (0.13±0.07) to (0.65±0.01) mg·kg-1dm; for Red Cracking BoleteXerocomuschryzenteronwere from (0.080±0.016) to (0.36±0.09) mg·kg-1dm and for King BoleteBoletusedulisfrom (1.2±2.4) to (4.9±1.4) mg·kg-1dm[15-20].The “background areas” in remote regions of Asia and soils and mushrooms there can experience impact of Hg from global fallout because of release of this element from the man-related sources[21-22].In edible pantropical mushroomMacrocybegiganteacollected from wild in Yunnan Province of China Hg contents in caps ranged from 0.48 to 1.78 mg·kg-1dm and in stipes from 0.36 to 1.70 mg·kg-1dm[23].

Table 1 Total Hg content (mg·kg-1 dm) of sclerotia of the fungus W.extensa from Yunnan

Notes: *Each value is mean of 3～4 determinations (mean ±SD)

A hymenophore when compared to the rest of fruit body of mushroom contains or is contaminated more with Hg, but there are fewer data on occurrence of Hg in edible, medicinal and nutraceutical mycelium/sclerotia in mushrooms[3,11].Sclerotia of saprophytic mushroomPleurotustuber-regiumcollected from several places in Nigeria where it is eaten “as a delicacy and as a meat substitute in soups, especially when rolled into dumplings” and “as thickener in native soups because of its good swelling properties“ or used as traditional medicine, showed a wide range of Hg content.Concentrations ranged from 0.003 3 to 0.18 mg·kg-1dm, while the mean and median values ranged from 0.024～0.048 and 0.013～0.040 mg·kg-1dm respectively, which are twice to fourfold higher compared toW.extensain the present study[3, 8].

Mushroom species show high variation in their ability to sequester Hg in fruit bodies and Hg chemical form in substrata can impact absorption and rate of sequestration[12,24].The absolute values of Hg content in sclerotia ofW.extensavaried between places in Yunnan (Table 1) and no relationship was found with the site’s altitude above the sea level and its geographical latitude.The assessed intake of mercury by adult who eats 50 g of sclerotia contained in the “Fulingjiabing” snack would be between 0.000 009 2 and 0.000 55 mg per capita or between 0.000 003 4 and 0.000 016 mg per kg body mass for a typical adult of mass 60 kg, which is a low intake.

Two important factors can be considered that can influence both intake and risk of Hg contained in edible fungal products.One is the impact of cooking (blanching) and other is decocting (makingdecoctum) in case of medicinal mushrooms and the corresponding selenium (Se) content, considering the fact that Se has a protective role against the toxic actions of Hg contained in foods and medicines.From available literature no data could be found on the selenium content of sclerotia or fruit bodies ofW.extensafungus[25-26].Available information on the impact of blanching (keeping in boiling water for 10 minutes) showed that this reduced Hg content of fruit bodies of mushrooms Bay Bolete (Boletusbadius) and Tawny GrisetteA.fulvaonly by 10%～20% compared to the Hg content of their original dried fruit bodies without blanching[27-28].These data suggested the occurrence of Hg in flesh of mushrooms largely in the form of compounds hardly soluble in water.If the clinical dosage of the sclerotia ofW.extensadosage is up to 45 g and assuming that a decocted medicinal formulation was prepared, the procedure is similar but less rigorous compared to blanching, the content of leached Hg in the decoct could be as little as 10%～20% of its original content in the medicinal substrate.Hence, Hg intake could be even lower when compared to eating the “fulingjiabing” snack.

Mercury content of sclerotia ofW.extensafrom the Yunnan land varies between the places the mushroom emerged and is not attributed to the site location above the sea level or the sites geographical location.An estimated intake of Hg from 50 g of sclerotia from the “fulingjiabing” snack gives exposure below health based intake values.Also assessed intake of Hg that could leaching into decocted medicine formulation made of sclerotia showed no health risk from this element.

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[21] Zhang H, Yin RS, Feng X B, et al.Sci.Rep., 2013, 3: 3322, doi: 10.1038/srep03322.

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O657.3

A

云南省不同產(chǎn)地茯苓菌核中汞元素含量研究

Anna Wiejak1，王元忠2，張 霽2，Jerzy Falandysz1*

1.University of Gdańsk, Gdańsk PL 80-308，Poland 2.云南省農(nóng)業(yè)科學(xué)院藥用植物研究所，云南 昆明 650200

茯苓菌核在亞洲具有悠久的藥用歷史，也是北京傳統(tǒng)小吃“茯苓夾餅”原材料。研究旨在測(cè)量和評(píng)價(jià)中國(guó)云南地區(qū)茯苓菌核的總汞含量。與其他種類蘑菇子實(shí)體相比，茯苓菌核汞含量較低。汞含量(干物質(zhì))的范圍為0.004 1～0.019 mg·kg-1，中位數(shù)為0.011 mg·kg-1，總體平均值為(0.011±0.004) mg·kg-1，表明云南不同產(chǎn)地茯苓菌核中Hg含量受到復(fù)雜山地類型的影響較大。對(duì)每天食用含有50 g茯苓菌核的茯苓夾餅Hg攝入量進(jìn)行健康評(píng)估，人均每天Hg攝入量為0.000 003 4～0.000 016 mg·kg-1，按成人體重60 kg計(jì)算，人均每天Hg攝入量為0.000 009 2～0.000 55 mg。研究結(jié)果顯示，茯苓菌核中Hg元素含量較低，其攝入量低于健康限量標(biāo)準(zhǔn)。同時(shí)，煎煮后的茯苓菌核中Hg攝入量也低于健康限量標(biāo)準(zhǔn)，由茯苓菌核制成的茯苓夾餅Hg含量較低。

生物富集；重金屬；真菌；野生食品

2014-10-15，

2015-01-25)

Foundation item：the National Natural Science Foundation of China (31460538, 31260496)

10.3964/j.issn.1000-0593(2016)09-3083-04

Received：2014-10-15; accepted：2015-01-25

Biography：Anna Wiejak, (1992—), female, PhD student of University of Gdańsk e-mail: anna.maria.wiejak@gmail.com *Corresponding author e-mail: jerzy.falandysz@ug.edu.pl

*通訊聯(lián)系人