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Abstract
Evaluation of Physical Properties of Benjakul Decoction and the Possibility of Contamination with
Heavy Metals
†
Natthida Weerapreeyakul*, Bung-orn Sripanidkulchai*, Supatra Chadbunchachai , Pennapa Subcharoen ‡
*Center of Research and Development in Herbal Health Products, Faculty of Pharmaceutical Sciences, Khon Kaen
†
‡
University, Faculty of Pharmaceutical Sciences, Khon Kaen University, Department for Development of Thai
Traditional and Alternative Medicine, Ministry of Public Health
This study involved an evaluation of the physical properties of the Benjakul decoction, the Sa-Moure-
Pak recipe (equal proportions) based on the Sa lung and Baht formulae. It was aimed at achieving basic
information for users. The raw herbal materials were placed in either a clay pot or beaker for comparison.
Water was added just to cover the herbs and boiled until the volume of liquid was one third of the original. It
was found that the volume used could differ depending on the size of the container selected and the water
volume used to cover the herbs. The boiled herbal solution in the beaker gave a more intense color and a
higher acidic pH compared with the pre-boiling mixture (p<0.05). When immersing the herbs in water for 60
minutes, the herbal solution showed more intense color and more acidity compared with pre-immersion, but
the acidity of the herb-immersed solution was less than that produced by the boiling method. Boiling the
mixture in the clay pot produced a clear color and more basic pH. However, the pH of the water before and
after boiling in the clay pot was found to be similar and was basic (pH ~ 8-9). When boiling herbs following the
Sa lung and Baht protocols in a clay pot, the color of the herbal solution was more intense and more acidic
than at pre-boiling (p<0.05). However, the acidity of the boiled herbal solution in the clay pot was less than
that in beaker. This demonstrated that the clay pot could absorb twice as much water as the clay pot that was
previously soaked in water overnight and allowed to dry in the air before use. The raw herbal materials were
also found to absorb water such that their weight increased two-fold after boiling. There was no fungal
contamination of the boiled herbs or the solution. However, such contamination was found in herbs and
solution that were not boiled after keeping them in a refrigerator for one week. The amounts of heavy metals,
i.e., lead, cadmium and arsenic, found in the raw herbal materials and in the clay pot were in trace amounts
and less than the limits set in the Thai Herbal Pharmacopoeia II. In conclusion, the decoction produces a
higher yield of substances from herbs and helps eliminate fungal contamination that might be present in
herbal materials and containers, or occur in the process of preparation.
Key words: decoction, Benjakul, physical properties, heavy metal contamination