Chemical profiles, antioxidant activity and acute toxicity of raw and sulfur-fumigated Smilacis Glabrae Rhizoma

Ethnopharmacological relevance: Smilacis Glabrae Rhizoma (SGR), known as Tu-fu-ling in the China, Japan and Korea, is an herb that has been used for clearing damp and detoxification in traditional Chinese medicine for many years. The post-harvest drying of SGR has traditionally been done by the sun, but sometimes sulfur fumigation is used instead due to its low cost and high efficiency. Recent reports show that sulfur fumigation can change the chemical constitution of herbal medicines and decrease their biology activity.

Aim of the study: This study will investigate the changes to the chemical constitution, acute toxicity and antioxidant potential of SGR that occur after sulfur fumigation. To date, no studies have investigated these aspects simultaneously.

Materials and methods: An ultra-performance liquid chromatography fingerprint method was developed for analysing changes to SGR's chemical constitution caused by sulfur fumigation. The chromatography conditions were as follows: all samples were analysed on a Waters Acquity UHPLC HT3 C18 column; the linear gradient elution was conducted with a mobile phase prepared from acetonitrile and water. All calibration curves showed good linear regression (R > 0.9991) within the tested range. The method was validated for precision, accuracy, limit of detection and quantification. Total flavonoids of the raw and sulfur-fumigated samples were also determined by ultraviolet spectrophotometry. The antioxidant properties of the extracts were evaluated using both DPPH and ABTS radical scavenging assays. The acute toxicities of the raw and sulfur-fumigated samples were investigated.

Results: The results demonstrate that the amounts of astilbin, neoastilbin, neoisoastilbin, isoastilbin, resveratrol and total flavonoids were lower in sulfur-fumigated samples than in raw samples. The antioxidant activity of the sulfur-fumigated samples was also significantly lower. Therefore, sulfur fumigation may cause chemical transformation, alter the chemical constitution, and decrease the bioactivity of SGR. Orally-administered doses did not cause mortality or changes in the general behaviour of tested mice. The LD50 was > 5000 mg/kg DW. However, the high-dose S-SGR mice had significant liver damage and high levels of plasma biochemical parameters (ALT, AST, DBIL, TBIL).

Conclusions: The results of the current study suggest that sulfur fumigation can decrease antioxidant activity in vitro; and that orally-administrated S-SGR is unsafe at doses > 3000 mg/kg dried materia medica. Therefore, sulfur-fumigation processing should be forbidden for SGR until its efficacy and safety has been demonstrated. An alternative method of sulfur fumigation for the post-harvest processing of SGR should also be developed.