Analytical Development Laboratory, United States Pharmacopeia, Rockville, MD, 20852, United States.
Dietary Supplements and Herbal Medicines, United States Pharmacopeia, Rockville, MD, 20852, United States.
J Pharm Biomed Anal. 2021 May 30;199:114063. doi: 10.1016/j.jpba.2021.114063. Epub 2021 Apr 6.
The demand and sales of dietary supplements derived from maca (Lepidium meyenii) have skyrocketed in the last decade and a variety of related nutritional and healthcare products have mushroomed into a business with market prominence. However, the lack of standard testing protocols for quality control could jeopardize the immediate benefits of these products for public health. We describe herein the development of analytical procedures for the determination of glucosinolates (GLs), the biologically active ingredients in maca. Because of the high polarity and instability caused by enzymatic hydrolysis, GLs in maca have been exclusively analyzed using desulfated GLs. This indirect analysis requires additional sample preparation steps, which is labor-intensive, and may lose the original GLs and introduce artificial compounds. Furthermore, the reported GL profiles of maca are inconsistent and incomplete, some GLs may be structurally misidentified. In this context, we focused on direct analysis of intact GLs in maca without the enzymatic desulfation. Four GLs (sinalbin, glucolepigramin, glucolimnanthin, and glucotropaeolin) were identified as the major GLs in maca root powder. An HPLC method based on ion pair chromatography was developed to determine individual and total GLs; chromatographic separations were achieved on a Luna column (C18, 4.6 × 100 mm,3 mm) using 0.1 % TFA in water and in methanol as mobile phase in a gradient elution mode. The developed procedures were validated within the calibration range of 10-500 μg/mL. Inter- and intra-day precision were shown to be lower than 3% at all concentrations levels with recovery between 100.2 % and 103.3 %. The procedures were applied to a total of 42 maca root powder products from 11 manufacturers. Sample analysis revealed a consistent correlation of glucotropaeolin: glucolimnanthin (1: 0.19) across all products with a correlation coefficient of 0.994. The correlation in combination with total GL contents for each product could be used for authentication and GL content determination. Incorporation of the developed procedures into USP monographs will strengthen the public standards for maca powder dietary supplements.
过去十年中，源自玛咖（Lepidium meyenii）的膳食补充剂的需求和销售呈爆炸式增长，各种相关的营养保健品和医疗保健品如雨后春笋般涌现，成为具有市场影响力的产业。然而，缺乏质量控制的标准检测协议可能会危及这些产品对公众健康的即时效益。我们在此描述了用于测定玛咖中生物活性成分——硫代葡萄糖苷（GLs）的分析程序的开发。由于酶解引起的高极性和不稳定性，玛咖中的 GLs 一直仅使用脱硫 GLs 进行分析。这种间接分析需要额外的样品制备步骤，既费力又可能会失去原始 GLs 并引入人工化合物。此外，报告的玛咖 GL 图谱不一致且不完整，一些 GLs 可能结构上被错误识别。在这种情况下，我们专注于直接分析未经酶脱硫的完整 GLs。鉴定出马咖根粉中的四种主要 GLs （白芥子苷、葡萄糖苷、硫代葡萄糖苷和硫代葡萄糖苷）。建立了一种基于离子对色谱的 HPLC 方法来测定单个和总 GLs；在梯度洗脱模式下，使用 Luna 柱（C18，4.6×100mm，3mm），以 0.1%TFA 水溶液和甲醇作为流动相实现色谱分离。所开发的程序在 10-500μg/mL 的校准范围内进行了验证。在所有浓度水平下，日内和日间精密度均低于 3%，回收率在 100.2%和 103.3%之间。该程序应用于来自 11 家制造商的总共 42 种玛咖根粉产品。样品分析显示，所有产品中硫代葡萄糖苷：硫代葡萄糖苷（1：0.19）之间存在一致的相关性，相关系数为 0.994。这种相关性与每个产品的总 GL 含量相结合，可用于鉴定和 GL 含量测定。将所开发的程序纳入 USP 专论将加强玛咖粉膳食补充剂的公共标准。
