1. Introduction

The use of herbs and plants for medicinal purposes and the study of their use is called Herbalism or Herbology. Herbs are the basic source of herbal medicines but there are many herbs that are thought to have adverse effects on human health. [1]. Many herbal plants have been used for herbal medicines since ancient times such as Aloe vera, Marshmallow, Great burdock, Pot marigold, Gota kola, Chinese Yam, Siberian ginseng and Tea tree etc. Herbal products are used for various ailments as in Pakistan many branded herbal medicines are used by the people such as Anab is used for blood purifier, Arq-mako is anti-inflamatory, Dinar used for liver disorder, Saduri and Toot siah is used to treat cough etc. [2].

There are many advantages and disadvantages of herbal medicine. Before treating yourself with herbs or seeking advice from a qualified herbalist or naturopath, consider the pros and cons of herbal treatments and remedies [3].

1.1. Advantages: There are many advantages of herbal products such as their cost-effectiveness as compared to allotropic medicines, these have very little side effects, these have very easy access to a common person, these can be brought without a prescription etc.

1.2. Disadvantages: Herbal treatment is time consuming and requires patience, herbs contain various elements which they absorb through roots from soil, it may be noticeable that body chemistry of patients could not matches with the ingredients of the herbal products so it may cause allergy [4].

In spite of the advantages and benefits of the herbal medicines there are many reports that shows that herbal medicines have been contaminated with heavy metals. As the metals have low excretion rate when excreted into the kidney which have damaging effect on humans, even at very low concentrations. Heavy metals have a tendency to accumulate in the food chain, however, an increase in their uptake can become toxic. The main intention of current research is to investigate the content of heavy metals in herbal medicines due to these reasons. Other aim of this study is the inherent capacity for coming into being the risks of heavy metals present in herbal medicines based on the World Health Organization (WHO) standard limits. 
2. Materials and Methods

2.1. Materials
Herbal products were used in this research to assess the heavy metal concentration for the presence of cadmium, mercury, lead, arsenic, cuprum and zinc from their solutions prepared in distilled water. The quantity of herbal medicine analyzed were in the form of capsules, pallets, syrups, and pastes (majoons) frequently used in Punjab, Pakistan. The medicines were manufactured for analysis by wet digestion method treating them with nitric acid and perchloric acid.

2.2. Equipments and Instruments

Atomic Absorption Spectrometer (JIEBO, AA320N), Electrical oven (memert Celsius 2005), Hot plate (Lab Tech), Electrical balance (G.C 2102), Grinder (Frith pulverize He.2), De-ionizer, Whatman filter paper, Fume Hood.

2.3. Chemicals
Nitric acid (HNO₃), Perchloric acid (HClO₄), Hydrochloric acid (HCl), Hydrogen peroxide (H₂O₂), Chromic acid H₂CrO₄, Cadmium Nitrate Cd(NO₃)₂, Zinc granules Zn, Ferrous Ammonium Sulphate (NH₄)₂.Fe(SO₄)₂.6H₂O, Manganese chloride MnCl₂.2H₂O, De-ionized water. All reagents were analytical grade and contain very low concentration of trace metals. 
2.4. Sampling of Herbal Medicines

The branded herbal medicines were purchased from Jhang Bazar, a local market in the district of Punjab, Pakistan. The samples were mostly syrups and tablets as shown in Table 1. Only those samples were collected for the study which were famous among the public and extensively used as over the counter (OTC) products. OTCs are those medicinal products which can be used without the prescription of physician or pharmacist. The formulations collected were mostly manufactured by Qurshi, Hamdard manufacturer and some other well-known herbal industries.

The list of the twenty sampled herbal medicines is given below in the table.

3. Results

The level of concentration of heavy metals in the herbal medicines are given in Table 2. All the samples except Itreefal zamani (4.3 ppm) exceeded the permissible limit for lead (5 ppm). Cr was analyzed in 90 % of the samples to have crossed the admissible amount (30-35 ppm) whereas Ni concentration exceeded the permissible limit (1.5 ppm) in 18 samples except Allergex and Epitize. In the case of cadmium, 19 products (i.e., 95 %) go above the admissible range (0.5 ppm). Mn, Zn and Fe were discovered within the allowed range in all the samples.

The highest Pb concentration was found in Ambreena tonic (31.7 ppm) followed by Hab moqil khas (31.2 ppm), Deedani (31.00 ppm), Jawahar mohara khas (30.2 ppm) and Akseer e jigar (29.5 ppm). The concentration of Cd was 3.2 - 83.2 ppm with the highest concentration in Itreefal zamani (83.2 ppm), followed by Zarjam (81 ppm), Bukhareen (9.5 ppm), Ambreena tonic (9.3 ppm), Akseer e jigar (8.2 ppm), Deedani (7.9 ppm) and Majoon sang dana murgh (6.8 ppm). These values depict that all the samples crossed the upper limits of the admissible range for Cd.

The highest amount of Cr was found in Ambreena tonic (141.2 ppm) followed by Majoon sang dana murgh (140.3 ppm), Deedani (137.2 ppm), Allergex (136.3) and Akseer e jigar (135.4 ppm). The highest amount of Cu was discovered in Hab moqil khas (15 ppm) followed by Khameera abresham (14.1 ppm), Majoon sang dana murgh (7.8 ppm), Zarjam (7.3 ppm), Itreefal zamani (6.4 ppm), Jawahar mohara khas (5.9 ppm), and Ahmareen (5.1 ppm). Highest concentration of Iron was found in Hab moqil khas (601.8 ppm) and lowest concentration was found in Allergex (9.1 ppm).

4. Discussion 
The following advocated daily limits of some of the significant metals will help in the findings of this research study are given table 3. 

4.1. Lead 
Lead is one of the most toxic among toxic heavy metals. It enters the human body in various ways including inhalation, drinking water, ingestion of food polluted with lead and absorption by skin. It accumulates in the body has no known useful biological function [9]. It has adverse effects on various body systems such as the reproductive, renal, digestive, cardiovascular and immunological systems [10]. The concentration of lead in the tested products was in the range of 4.3 - 31.7 ppm. The recommended limit for finished herbal products is 5 ppm while for crude herbal material it is 10 ppm [11].

Since our study was conducted on finished herbal products, we consider the 5 ppm as the applicable limit. Thus, only one product out of the twenty samples assessed had lead concentration below the recommended limit. It is clear, therefore, that these products are potentially toxic to man. Incidentally, all these products are very popular among the people and adult and children chronically use some of them such as Hab e moqal khas and Majoon suranjan. There is a large body of data on the adverse effect of lead in herbal formulations human health [12].

4.2. Cadmium 
Cadmium is a toxic metal of occupational and environmental concern. Cadmium exposure leads to a variety of adverse effects due to its extremely long biological half-life. The rate of cadmium transfer from soil to plants is very high and the metal is considered to have carcinogenic effects on liver, pancreas and stomach [13]. Its recommended concentration in plant is 3 ppm while for finished plant products, it is 0.5 ppm [11]. The recommended consumption of cadmium is 70 μg/day [5]. Based on this, 19 products out of 20 exceeded the permissible limit. The highest Cd consumption are: Itreefal zamani (83.2 ppm), followed by Zarjam (81 ppm), Bukhareen (9.5 ppm) and Ambreena tonic (9.3 ppm).

4.3. Chromium 
Chromium is exists in two ionic forms, trivalent and hexavalent, the latter being toxic and is correlated to human carcinogenesis and acute toxicity of aquatic organisms [14]; on the other hand, its reduced form (trivalent) is an essential element for animals. The concentration of chromium was in the range of 9.5 - 141.2 ppm. There is no recommended limit for chromium in herbal finished products. The recommended limit of chromium is 11 - 25 μg/day for children and 30 - 35 μg/day for adults [6,7]. Highest consumption was observed for Ambreena tonic (141.2 ppm). Only two products had chromium concentration below the recommended limit. Such a high concentrations could be toxic due to the chronic use of some of the tested products.

4.4. Copper 
Copper has both beneficial and toxic effects depending on its level of consumption. Monitoring of copper limit is essential as it is beneficial in low concentrations but exhibit various toxic effects above the safety limit. In this study, copper was found in the products in the concentration range of 2.9 - 15 ppm. The recommended consumption of copper is 900 and 340 - 400 μg/day for adult and for child, respectively [6,7]. Thus, all the tested products were safe with regard to copper content.

4.5. Nickel 
Nickel is abundant in nature. Possible exposure sources of nickel are food, drinking water, absorption by contact and inhalation in nickel-polluted area [15]. Ingestion of large amounts of nickel affects stomach, liver, kidneys, immune system and reproduction in rats and mice [15]. The most common toxic effect is dermatitis while lung cancer has also been reported in some studies [15]. Nickel was found in a concentration range of 4.5 - 51.3 ppm. The highest concentration was found in Khameera Abresham (51.3 ppm), followed by Itreefal zamani (43.4 ppm) and Ambreena tonic (17.9 ppm). The recommended consumption limit of nickel is 35 μg/day [8]. Thus, almost all the tested samples exceeded the daily allowed limit for nickel. The contents of Mn, Zn and Fe in the tested products were within their permissible limits, they did not exceed the daily consumption limits of these metals.

5. Acknowledgement 
First of all, I want to say a special thanks to my honorable supervisor Prof. Dr. Iftikhar Hussain Bukhari, Ex-Chairman, Department of Chemistry, Govt. College University Faisalabad. During my academic activities at campus I found him a kind and generous person. His untiring guidance, unerring vigor, staunch help, masterly advices and inspiring stance at all time made it very easy to under this research and to bring it in present form.

It is my privilege to record my deepest sense of gratitude to my respected teachers Dr. Atta-ul-Haq, Asstt. Prof. for helping me to set this paper and Dr. Tanveer Hussain Bokhari, Asstt. Prof. Department of Chemistry, Govt. College University Faisalabad, for providing me help in preparing the review.

I want to express my special thanks to Mr Khalid Ahmad, owner Shahzad Dawakhana, Karkhana Bazar, Faisalabad for providing me finished herbal products on demand.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

I convey my special thanks to my sweet friends and research fellow Rabia Arshad who always encouraged and helped me during the course of my study and research period.

Last but not least, I express my profound admiration and deepest thanks to my supporting parents and my siblings Noreen, Imran, Adnan, Usman and Arsalan, who always stood behind me. It was only due to their moral support and financial help during my entire academic carrier that enabled me to complete my work efficiently and proficiently.

May ALLAH give them His blessings along happy life. Ameen

Figure 1: Heavy metal contents in first ten herbal medicines (as found on table. 2).

Figure 2: Heavy metal contents in last ten herbal medicines (as found on table. 2).

Table 1: Basic information about the herbal medicines.

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