Determination of Lead in Smilax luzonensis Herbal Preparations in Malaysia

Abstract

The DCA (Drug Control Authority) of Malaysia implemented the phase 3 registration of traditional medicines on 1 January 1992. As such, a total of 100 products in various pharmaceutical dosage forms of a herbal preparation containing Smilax luzonensis, either single or combined preparations, were analyzed for the presence of lead, using atomic absorption spectrophotometry. Results showed that 14% of the above products possessed 10.02 to 21.21 ppm of lead, and, therefore, they failed to comply with the quality requirement for traditional medicines in Malaysia (<10 ppm). Although this study showed that 86% of the products complied with the quality requirement for traditional medicines in Malaysia pertaining to lead, they cannot be assumed safe from lead contamination because of batch-to-batch inconsistency.

The use of traditional and alternative systems of medicine goes back beyond recorded history, but has increased tremendously in the last decades (MacLennan, Wilson, and Taylor 1996; Eisenberg et al. 1998; Woods 1999; Ernst and White 2000; Ernst 2000; Khan et al. 2001; Taha 2002; WHO 2002; Zaidi 2002; Saras 2003). However, the safety of their use has recently been questioned due to the reports of illness and fatalities (Stewart et al. 1999; Ernst 2002). Therefore, a critical evaluation of their safety is extremely important (Ernst 2000; Shamala 2001; Taha 2002).

In line with this, the Drug Control Authority (DCA), Malaysia, implemented the phase 3 registration of traditional medicines on 1 January 1992. The registration criteria for traditional medicines include the following: limits for heavy metals (Poison Act 1952; Revised 1989), limits of microbial contamination and the absence of steroids and other adulterants (Poison Act 1952; Revised 1989), limits of disintegration time (Pharmacopoeial Standards), claimed indications (Medicines Act, Advertisement and Sale, 1956; Revised 1983), prohibition of herbs with known adverse effects, prohibition of endangered animal species (Wildlife Protection Act, 1972) and compliance to GMP (Good Manufacturing Practice) and GSP (Good Storage Practice) (http://www.bpfk.gov.my/newst.htm).

In Malaysia, one of the herbal remedies is Smilax luzonensis, commonly known as akar banar, akar gadong tikus (DePadua, Bunyapraphatsara, and Lemmens 1999; Compendium of Medicinal Plants Used in Malaysia 2002), akar kelona betina, akar semenjoh ( Compendium of Medicinal Plants Used in Malaysia 2002), alik besi, banar (Kamarudin and Latiff 2002), banar babi (DePadua, Bunyapraphatsara, and Lemmens 1999; Compendium of Medicinal Plants Used in Malaysia 2002; Kamarudin and Latiff 2002), canar babi ( Compendium of Medicinal Plants Used in Malaysia 2002), gadong jantan ( Compendium of Medicinal Plants Used in Malaysia 2002; Kamarudin and Latiff 2002), gadong tikus, kelona betina, kijil, rancang tembaga, and semenjoh (Kamarudin and Latiff 2002). The rhizomes of this plant are used as sexual tonics (Kamarudin and Latiff 2002) and as such, there are various pharmaceutical preparations available in the Malaysian market.

Lead is a ubiquitous toxicant (Schroeder and Tipton 1968; Konat and Clausen 1974). Therefore, in the present study, we analyzed the lead content using atomic absorption spectrophotometry in a total of 100 products (both registered and unregistered with the DCA Malaysia) in various pharmaceutical dosage forms of S. luzonensis preparations, which were bought in the Malaysian market, after performing a simple random sampling on them, to enable each sample an equal chance of being selected (Schefler 1984) in an unbiased manner (Newman 1995).

MATERIALS AND METHODS

Instrumentation

GBC 906 AA model atomic absorption spectrophotometer complete with inbuilt Windows-based 906 program software was used in this study. The operating parameters were gas mixture: air-acetylene; flow rate of air: 10.0 L/min; flow rate of acetylene: 2 L/min; slit width: 1.0 nm; flame height: 10 cm; current: 5.0 mA; and wavelength: 217 nm.

Treatment of Glasswares

All glasswares were soaked with aqua regia (HCl:HNO₃ = 3:2) (Sastre et al. 2002) for 2 h and then washed with deionized water (Deionizer Elga B113).

Wet Digestion of Samples

A total of 100 different samples containing S. luzonensis (see Tables 1 and 2) were digested using aqua regia wet digestion. Coarse particles like tablets, pills or powders, capsules, and the contents were ground to fine powder or particles prior to digestion.

Approximately 1.5 g of the sample were weighed and placed in a 100 ml Quickfit round bottom flask and 25.0 ml of freshly prepared aqua regia was added. This mixture was then refluxed over a water bath for 6 to 8 h (or until all the samples had dissolved in the aqua regia). Later, they were allowed to cool and then filtered. The residue was washed with deionized water.

The combined aqueous extract was then made up to 50.0 ml with deionized water. This extraction procedure was repeated for the same sample (replicates) and the blank (containing aqua regia only). Two methods, calibration curve and standard addition methods, were used for the analysis.

Quantitative Analysis for Lead

Stock standard solution (1000 ppm) was diluted serially with deionized water to produce 0.5, 1, 2, 4, and 8 μg/ml lead. The absorbance was recorded and a calibration curve was produced from these concentrations.

Stock standard solution (1000 ppm) was diluted serially with deionized water to produce 1, 3, 5, and 10 μg/ml lead. Each of the above concentrations was added with 10 ml of diluted extract (obtained after wet digestion) and then analyzed as for the calibration curve.

RESULTS

Lead Determination

Tables 1 and 2 show that there is a general consistency in the results obtained between the calibration curve and standard addition methods. This is expected because the standard addition method is only used for checking the validity of another quantitative determination and is applicable when the absorbance-concentration relationship is linear for the particular standard solutions used (Aldous and Reynolds 1970). The sample absorbance had been corrected with the blank. In addition, the percentage difference between the two methods was <10%.

Results from the two tables show that 14 out of 100 products, viz. 14% of the products analyzed, possessed 10.02 to 21.21 ppm of lead, and therefore do not comply with the quality requirement for traditional medicines in Malaysia. The quality requirement for traditional medicines in Malaysia is not exceeding 10 ppm for lead (http://www.bpfk.gov.my/FAQ.htm; http://www.bpfk.gov.my/default.asp; Jaafar 1995). Out of these 14 products, three products, viz. Ace Capsule Rancang Tem-baga, Gold Box Rancang Tembaga Plus, and Maajun Pak Tani Rancang Tembaga, with 12.31 ± 2.32, 10.02 ± 3.26 and 12.31 ± 0.21 ppm of lead, respectively, in fact, have already registered with the DCA, Malaysia.

The rest of products, Super Capsule Rancang Tembaga, Great Capsule Rancang Tembaga, Tender Capsule Rancang Tembaga, Force Capsule Rancang Tembaga, Super Capsule Rancang Tem-baga Plus, Force Capsule Rancang Tembaga Plus, Jiwa Super Capsule Rancang Tembaga, Great Pill Rancang Tembaga, Tender Pill Rancang Tembaga, Extra Pill Rancang Tembaga, and Force Pill Rancang Tembaga, with 21.02 ± 3.43, 12.51 ± 1.23, 11.36 ± 1.45, 10.21 ± 0.71, 12.76 ± 0.24, 23.16 ± 1.23, 24.45 ± 1.23, 14.79 ± 1.85, 18.73 ± 1.78, 19.53 ± 2.79, and 18.53 ± 2.54 ppm of lead, respectively, however, have not registered with the DCA, Malaysia.

DISCUSSION

Although the phase 3 registration of traditional medicine was implemented on 1 January 1992, there are still many unregistered traditional medicines rampantly available in the Malaysian market with contaminations of heavy metals above the permissible limit (Taha 2002). In 2002, the DCA, Malaysia, tested 1056 traditional medicine samples, of which 17.7% failed to meet the quality requirements (http://www.bpfk.gov.my/newst.htm).

Although this study managed to show that 86% of the products complied with the quality requirement for traditional medicines in Malaysia pertaining to lead, they cannot be assumed safe from lead contamination because of batch-to-batch inconsistency (Ko 1998).

The common belief that traditional medicines, particularly the natural herbal remedies, are of natural origin and hence inherently safe (Friedman 1996; Ernst 1999) and without any adverse effects is sometimes unfounded (Ramli 2001). There have been numerous reports of adverse effects associated with traditional medicines and in particular herbal remedies. Poisonings associated with the presence of heavy toxic metals in medicinal plants were reported in Asia, Europe, and the United States (Dunbabin et al. 1992; Markowitz, Nenez, and Klitzman 1994; Olujohungbe, Fields, and Sandford 1994; Kakosy, Hudak, and Naray 1996). In addition, lead poisoning from traditional remedies mainly used for enhancing sexual performance have been been reported (Brearley and Forsythe 1978; Pontifex and Garg 1985; Dolan et al. 1991). This is important because lead has adverse effects on the male reproductive system (Quintanilla-Vega et al. 2000; Benoff et al. 2003).

Several possibilities may be responsible for the presence of heavy metals in herbal remedies. Firstly, the presence of heavy metals may be the result of accidental contamination during the manufacturing process, for instance, from grinding weights or lead-releasing containers or other manufacturing utensils (Koh and Woo 2000). As such, in line with GMP (Good Manufacturing Practice), it is advisable, where possible, to use stainless steel containers, utensils, and piping. Traditional medicine manufacturers must fulfill this requirement prior to being licensed by the DCA, Malaysia ( Newsletter of the Drug Control Authority Malaysia 2001).

Secondly, the medicinal herbs may contain heavy metals when grown in seriously polluted soil (Schilcher 1983; Kabelitz 1998; McLaughlin, Parker, and Clark 1999), water or air (McLaughlin, Parker, and Clark 1999). In addition, it was reported that the contamination of plants with lead depends on several factors, e.g., traffic densities and distance from the road (Bosque et al. 1990) and proximity to roadways or metal mining and smelting operations (Pip 1991). In addition, high levels of toxic metals can be found when fertilizers, organic mercury, or lead-based pesticides contaminate irrigation water (Abou-Arab et al. 1999).

Besides these, some of the combined herbal remedies may also contain animal, mineral, or any other excipient that may also be contaminated with heavy metals (Chuang et al. 2000). Lastly, lead poisoning may be the result of continuous exposure to lead-containing materials in an industrial setting (Winship 1989).

Therefore, the DCA, Malaysia, has specified that the validity of registration of pharmaceutical products (nonpoisons) to be limited to a maximum of 5 years. Applicants will have to submit application for reregistration for the reassessment of the quality, efficacy, and safety of their products. In addition, the DCA may reject, cancel, or suspend the registration of any product if deemed necessary ( Newsletter of the Drug Control Authority Malaysia 2001).