Differentiation of three Asparagus species by UHPLC-MS/MS based molecular networking identification and chemical profile analysis

Abstract

Asparagi Radix (AR), a traditional Chinese medicine, is the dried roots of Asparagus cochinchinensis (Lour.) Merr. Modern pharmacological studies have shown that AR has various excellent bioactivities, such as antioxidative, antitumor, antibacterial, anti-inflammatory, and hypoglycemic effects. However, the quality control method of AR is incomplete and there are various AR adulterants in markets due to their similar morphological characters. Here, holistic and practical quality evaluation methods were developed to chemically distinguish three common Asparagus species in markets, including Asparagus cochinchinensis (Lour.) Merr., Asparagus officinalis L., and Asparagus lycopodineus (Baker) F.T.Wang & Tang. The chemical constituents of three species were rapidly tentatively annotated using a combination of ultra-high pressure liquid chromatography-linear ion trap-orbitrap high resolution mass spectrometry (UHPLC-LTQ-Orbitrap-MS) and molecular networking (MN). Fifty-six steroidal saponins were annotated, including common and characteristic chemical constituents of the three Asparagus species. Besides, to establish holistic and practical methods to differentiate three Asparagus species, an HPLC-ELSD (evaporative light scattering detector) was applied for fingerprint analysis and content determination of the sum of protoneodioscin and protodioscin of twenty samples. Each Asparagus species showed characteristic chemical profile and AR showed much higher level of the sum of protoneodioscin and protodioscin than that in the others. The above analyses showed that the three Asparagus species mainly contain steroidal saponins and the developed HPLC-ELSD profile of saponin can be used to differentiate them. In conclusion, this study reveals the different chemical constituents of three Asparagus species and provides relatively feasible quality evaluation methods for them which are essential for the rational utilization of these Asparagus species.