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Journal of soil science and plant nutrition

versión On-line ISSN 0718-9516

J. Soil Sci. Plant Nutr. vol.12 no.3 Temuco set. 2012  Epub 31-Ago-2012

http://dx.doi.org/10.4067/S0718-95162012005000008 

Journal of Soil Science and Plant Nutrition, 2012, 12 (3), 463-470

 

Determination of mineral contents of Digitalis purpurea L. and Digitalis lanata Ehrh

 

J.S. Negi1, V.K. Bisht1, A.K. Bhandari1 and R.C. Sundriyal1*

1 Herbal Research and Development Institute, Mandal, Gopeshwar (Chamoli) 246 401, Uttarakhand, India
*Corresponding author: sundriyalrc@yahoo.com, negijs@yahoo.com


Abstract

Digitalis purpurea and Digitalis lanata are commonly used in treatment of heart diseases, the species has recently introduced for cultivation in the state of Uttarakhand, India. The mineral contents of cultivated plants of these species have to be within permissible limit for its effectiveness. Using inductively coupled plasma mass spec-trometry (ICP-MS), this paper describes analysis of selected minerals [viz. Boron (B), Chromium (Cr), Manganese (Mn), Cobalt (Co), Nickel (Ni), Copper (Cu), Arsenic (As) and Lead (Pb)] in various plant parts of D. purpurea and D. lanata at pre- and post flowering stages. Our results revealed that the concentration of B, Cr, Mn, Co, Ni, Cu, As and Pb as 8.16±0.04 to 27.18±1.11, 7.30±0.03 to 21.16±0.20, 62.69±1.45 to 247.27±5.29, 0.65±0.08 to 6.13±0.05, 9.19±0.01 to 16.15±0.05, 0.02±0.0 to 25.27±0.20, 0.83±0.04 to 4.98±0.06 and 4.70±0.02 to 8.19±0.04 ug g1Î, respectively. The study reports that the mineral contents were well within the permissible range for medicinal uses. Therefore, the species are recommended for large scale cultivation.

Keywords: Mineral elements, ICP-MS, Microwave Digestion, Digitalis purpurea, Digitalis lanata, Scrophulariaceae.


1. Introduction

Minerals present in medicinal plants are of great imÎ portance to understand their pharmacological actions (Serfor-Armah et al., 2002). Mineral elements play an important roles in chemical, biological, biochemical, metabolic, catabolic and enzymatic reactions in the living organism which will lead to the formation of active organic constituents (Serfor-Armah et al., 2001). Their deficiency causes diseases, whereas the excess presence may cause toxicity (Hashmi et al., 2007). Mineral contents of several medicinal plants have been determined by applying several techniques such as atomic absorption spectroscopy (Negi et al., 2010), atomic emission spectrometry (Razic et al., 2003), electrothermal atomic absorption spectrometry (Gomez et al., 2004), X-ray emission (Mohanta et al., 2003), X-ray fluorescence (Salvador et al., 2003), inÎ ductively coupled plasma mass spectrometry (Falco et al., 2003) and neutron activation analysis (Yamashita et al., 2005).

Digitalis purpurea and D. lanata (family Scrophulariaceae) are reported to contain various cardiac and steroidal glycosides localized in roots and leaves (Lungeanu et al., 1963). Digitoxin is the main active constituent of these species (Hiermann et al., 1977). These species are used in the treatment of heart failure (Reddy, 2010), and extracts are reported to perform cardiovascular (Navarro et al., 2000), antitumour (Lopez-Lazaro et al., 2003), antimicrobial (Benli et al., 2009) and antiinflammatory activities (Nikolov et al., 1962). There are many reports on organic constituents of the genus Digitalis, however little attention has been given to analyze their mineral contents (Roca-Perez et al., 2006). Because of high market demand these species have been introduced for cultivation in the state of Uttarakhand, India, in recent years and successfully grown at farms with excellent biomass and seeds production capacity. It is important to analyze the mineral contents of these species before recommending them for large scale cultivation and medicinal uses. Considering that, present study was designed to analyze the mineral elements viz, Boron (B), Chromium (Cr), Manganese (Mn), Cobalt (Co), Nickel (Ni), Copper (Cu), Arsenic (As) and Lead (Pb) in different parts of D.purpurea and D. lanata that are raised in farms of Herbal Research and Development Institute.

 

2. Materials and methods

2.1 Plant Sample Collection and Processing

For analysis of mineral contents of two Digitalis species (viz. D. purpurea and D. lanata), the plant samples were collected at pre- and post flowering stages from herbal garden of Herbal Research and Development Institute, Gopeshwar, Uttarakhand, India. For each stage samples were collected from three different places of same population with nearly same maturity. The samples were separately air dried and grinded to powder of homogenized particles. Samples (0.5 g each) were taken and transferred to acid washed teflon PFA digestion tubes separately. Thereafter 10 ml of concentrated HNO3 and H2SO4 (4:1) was added and the tubes were heated in a microwave oven using digestion program (Table 1) in microwave digesÎ tion system (Aurora MW 800). After completion of digestion all the samples were cooled for about 1 hour. The digested samples were transferred to 100 ml acid washed volumetric flask and make up the volume using demineralized water (Millipore). Thereafter the samples were filtered and stored in polypropylene flasks prior to analysis.

2.2 Preparation of Standard Solutions

Multielement working standard solutions (50, 100, 150, 200 μg/l) were prepared by appropriate dilution of the stock ICP multielement standard (Merck) 10000 μg/l. All analyses were performed on ICP-MS (Perkin Elmer NexION 300X) using both Standard and Kinetic Energy Discrimination (KED) modes. The operating conditions for the ICP-MS are summarized in Table 2. All standard solutions and digested samples of both Digitalis species were run one by one. The calibration curves were obtained using NexION software. The data were arranged in tabular form using standard deviation.

3. Results and discussion

The concentration of B, Cr, Mn, Co, Ni, Cu, As and Pb analyzed in different plant samples of two Digitalis species are presented in Table 3. The concentration of essential minerals (B, Cr, Mn, Co, Ni and Cu) in the studied samples were found to be higher than the toxic ones (As and Pb). It was estimated that the conÎ centration of most of the minerals was higher at post flowering stage than that of pre flowering stage. The concentration of boron ranged between 8.16±0.04 to 27.18±1.11 μg/g, which was higher in the leaves of D. lanata. The B content was higher in post flowering stage than the pre flowering stage except for roots of D. perpurea where it exhibited reverse stand (Table 3). Among the studied species the leaves of D. lanata had higher concentration than the leaves of D. perpurea. Contrarily roots of D. perpurea had higher B concentration than the roots of D. lanata. In medicinal plants, WHO (2007) limits had not yet been established for B, however, Krejcova and Cernohorsky (2003) found the range of B between 2.71±0.13 to 27.7±0.9 mg/kg in tea and coffee samples. Comparison of our results with these findings clearly shows that our results are well within the range. In case of chromium, leaves and roots of D. perpurea at post flowering stage comÎ prised higher concentration, whereas for D. lanata the Cr concentration more or less at pre- and post-flowering stages (Table 3). There is no set limit for Cr in medicinal plants by WHO, however in Canada 2 ppm permissible limit was set for raw medicinal plant material (WHO, 2007). Ashraf et al. (2010) estimated the range of Cr between 1.325 to 28.28 ppm in Artemisia maritime and A. turanicum. Comparison of our results with these findings clearly shows that our results are also within the range. Interestingly for manganese the leaves comprised higher concentration at pre flowering stage, whereas for roots the Mn concentration was higher at post flowering stage for both species. From this study, it is concluded that roots of both species are rich source of Mn at post flowering stage and leaves at pre flowering stage. For medicinal plants, WHO (2007) limits have not yet been established for Mn.

The concentration of cobalt was higher in D. perpurea than in D. lanata (Table 3). Among plant parts it was estimated higher at post flowering stage for D. perpurea. Contrarily, for D. lanata the concentration was higher in pre flowering stage for both plant parts (Table 3). Cobalt is an important component of vitamin B12 which participates as a coenzyme in various enzymatic reactions (Berdanier, 1994). For Co there is no set limit for their concentration in medicinal plant. The nickel content was more or less similar among plant parts as well as among species. The permissible limit for Ni is not established by WHO, although, daily dietary intake for Ni is estimated to be 100 μg/day. Ni deficiency is rare in humans as Ni requirements are low and availability high from dietary sources. Nickel deficiency causes depressed growth, reproductive changes and altered lipid and glucose levels in the blood (Onianwa et al., 2000). The copper content was minimal in roots particulary at post flowering stage in both the species. Among species Cu content was higher in D. lanata than D. perpurea (Table 3). Copper has been recognized as an essential element for living organism due to its presence in important proteins and enzymes (Onionwa et al., 2001). Cu deficiency in humans caused bone demineralization, depressed growth, depigmentation, gastrointestinal disturbances, dermatitis and neurological disorders, while, excessive intake has been reported to cause liver cirrhosis and toxicity (Reynold et al., 2008). Thus Digitalis roots and leaves can be used to compensate Cu deficiency. The permissible limit set by WHO in edible plants is 3 ppm. After comparison of the metal limit in the studied plants with those proposed by WHO, it was found that most of the samples accumulates Cu above this limit. However, for medicinal plants, the WHO (2007) limits had not yet been established for Cu. Al though in medicinal plants, permissible limits for Cu set by Singapore was 150 ppm (WHO, 2007). Reddy and Reddy (1997) pointed out that the range of Cu contents in the 50 medicinally important leafy material growing in India were 17.6 to 57.3 ppm.

 

The two toxic minerals also exhibited different level of concentration among different plant parts as well as different plant stage. The arsenic content was higher in D. perpurea than in D. lanata and was higher in roots than leaves (Table 3). The lead content was estimated higher in root parts than leaves for both species. The concentration of Pb decreased in leaves and roots at post flowering stage except for roots of D. perpurea where it exhibited reverse stand. Arsenic is considered as toxic mineral, however it exhibits beneficial actions in low quantities as it affects taurine and polyamine formation in plasma and tissues. The permissible limit for As and Pb in herbal medicines and products are 5 and 10 mg/kg, respectively (WHO, 2007). Our values are lower than these showing good qualities of material. The data through ICP-MS provides more accurate estimation than other techniques. Therefore, implications of our values are high for suggesting plant material for medicinal uses.

 

4. Conclusion

The microwave digestion method has considerable advantages, which includes good precision and accuracy, reduced contamination, speed and safety. The uses of concentrated nitric acid and sulfuric acid (4:1) mixtures allowed the complete digestion of samples. Mean intake of B, Cr, Mn, Co, Ni, Cu, As and pb are falls within the recommended range. The results obtained showed significant differences among the elemental concentrations in both species of Digitalis. The mineral contents were well within the permissible range for human consumption, therefore, recommended for medicinal uses. It is also suggested that large scale cultivation of these species may be promoted in the state.

 

Acknowledgments

The authors are thankful to Agriculture and Processed Food Products Export Development Authority, Ministry of Commerce and Industry, Govt. of India, provided financial support for equipments (Grant no. FLR/059/2006-07/13692). Thanks are also to Director, HRDI for providing facilities.

 

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