UFLC-PDA-MS/MS Profiling of Seven Uncaria Species Integrated with Melatonin/5-Hydroxytryptamine Receptors Agonistic Assay

Natural Products and Bioprospecting (2020) 10:23–36 https://doi.org/10.1007/s13659-020-00230-8 ORIGINAL ARTICLE UFLC‑PDA‑MS/MS Profiling of Seven Uncaria Species Integrated with Melatonin/5‑Hydroxytryptamine Receptors Agonistic Assay Jian‑Gang Zhang1 · Xiao‑Yan Huang1 · Yun‑Bao Ma1 · Ji‑Jun Chen1,2 · Chang‑An Geng1 Received: 5 December 2019 / Accepted: 6 January 2020 / Published online: 13 January 2020 © The Author(s) 2020 Abstract Uncariae Ramulus Cum Uncis (Gou-Teng), the dried hook-bearing stems of several Uncaria plants (Rubiaceae), is a wellknown herbal medicine in China. The clinical application of Gou-Teng is bewildered for the morphological and chemical similarity between different species. In order to discern their chemical and biological difference, an ultra-fast liquid chromatography equipped with ion trap time-of-flight mass spectrometry (UFLC-IT/TOF-MS) combining with melatonin (MT1 and M T2) and 5-hydroxytryptamine (5-HT1A and 5-HT2C) receptors agonistic assay in vitro was conducted on seven Uncaria species. As a result, 57 compounds including 35 indole alkaloids, ten flavonoids, five triterpenoids, five chlorogenic analogues, and two other compounds were characterized based on their MS/MS patterns and UV absorptions. Specifically, cadambine-type and corynanthein-type alkaloids were exclusively present in U. rhynchophylla and U. scandens, whereas corynoxine-type alkaloids were commonly detected in all the seven Uncaria plants. Three Uncaria species, U. rhynchophylla, U. macrophylla, and U. yunnanensis showed obviously agnostic activity on four neurotransmitter receptors (MT1, MT2, 5-HT1A, and 5-HT2C). This first-time UFLCMS-IT-TOF analyses integrated with biological assay on seven Uncaria plants will provide scientific viewpoints for the clinical application of Gou-Teng. We dedicate this paper to Prof. Sun Han-Dong on the occasion of his 80th birthday. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13659-020-00230-8) contains supplementary material, which is available to authorized users. * Chang‑An Geng 1 State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Yunnan Key Laboratory of Natural Medicinal Chemistry, 132# Lanhei Road, Kunming 650201, Yunnan, People’s Republic of China 2 University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China 13 Vol.:(0123456789) 24 J.-G. Zhang et al. Graphic Abstract Keywords Uncariae Ramulus Cum Uncis · Uncaria plants · LCMS-IT-TOF analyses · Melatonin and 5-hydroxytryptamine receptors 1 Introduction Uncariae Ramulus Cum Uncis (Gou-Teng), the dried hookbearing stems of Uncaria plants (Rubiaceae), is a wellknown traditional Chinese medicine (TCM), which has long been used for the treatment of hypertension, fever, headache, dizziness, stroke, and bilious disorders in China [1–4]. In addition to monotherapies, Gou-Teng is also prescribed in many formulae, such as Diao-Teng San (Cho-Deung-San in Korean and Choto-san in Japanese) and Yi-Gan San (Yokukansan in Japanese) [2]. Indole alkaloids as the characteristic constituents of Uncaria plants are responsible for the hypotensive effects, e.g. rhynchophylline and hirsutine showing antihypertensive and antiarrhythmic effects [5, 6]. According to the latest Chinese Pharmacopoeia (2015 edition), five Uncaria plants, namely Uncaria rhynchophylla (U. r), Uncaria macrophylla (U. m), Uncaria sinensis (U. si), Uncaria hirsuta (U. h), and Uncaria sessilifructus (U. se), are documented as the official resource of Gou-Teng [7]. Furthermore, several Uncaria plants, e.g. Uncaria scandens (U. sc), Uncaria laevigata (U. l), and Uncaria yunnanensis (U. y), are also used as the substitutes of Gou-Teng in prescriptions [8, 9]. Although recent studies have manifested the antidepressant-like effects of U. rhynchophylla and U. lanosa, and locomotor decreasing effects of U. rhynchophylla, U. macrophylla, and U. sinensis [10–12], few reports can discern the difference regarding the chemical profiles 13 and biological activities between different Uncaria species. Thus, the clinical application of Gou-Teng is bewildered for the morphological and chemical similarity between different Uncaria plants. Different from the cardiovascular effect, the psychiatric property and active constituents of Gou-Teng are still disputed. Melatonin (MT) and 5-hydroxytryptamine (5-HT) receptors are two types of neurotransmitter receptors closely related to mental diseases [13–16], and thus are used to evaluate the psychiatric effects of different Uncaria plants. The present study applied an ultra-fast liquid chromatography equipped with ion trap time-of-flight mass spectrometry (UFLC-IT/TOF-MS) and combined with melatonin and 5-hydroxytryptamine receptors agonistic assay to discern seven Uncaria species regarding their chemical profiles and psychiatric properties. 2 Results and Discussions 2.1 LCMS‑PDA Analyses Seven Uncaria plants were analyzed by UFLC-PDA-MS/ MS to provide their respective base peak chromatograms (BPCs) in both positive and negative modes (Fig. 1). In total, 57 compounds including 35 indole alkaloids, ten flavonoids, five triterpenoids, five chlorogenic acids, and two UFLC-PDA-MS/MS Profiling of Seven Uncaria Species Integrated 25 Fig. 1  Base peak chromatograms (BPCs) of seven Uncaria plants in positive (1 BPC) and negative (3 BPC) modes 13 26 other compounds were characterized according to their UV absorptions, MS/MS fragmentations, retention time, and comparing with the reported compounds (Table 1). 2.1.1 Indole Alkaloids Indole alkaloids are the characteristic constituents in Uncaria plants with high response in positive mode MS. In this investigation, a number of 35 indole alkaloids were described and divided into six subclasses including cadambine-type (19, 21, 23, 26, 47), vinsosamide-type (15), D-seco-type (18, 25, 33, 38, 44, 50), corynoxine-type (11, 20, 22, 24, 27, 28, 31, 32, 34, 35, 36, 37, 42), corynantheintype (40, 43, 45, 48, 51, 53, 55, 57), and ajmalicine-type (39, 54). In accordance with the previous investigation [17], D-seco alkaloids commonly generated the characteristic fragmentation ions ascribed to the loss of 17 Da (NH3) in the MS2 experiment; the indole and oxindole alkaloids could be differentiated from their respective maximal UV absorptions around 280 nm (indole) or 240 nm (oxindole); the numbers and types of glycosyl moieties were determined by the mass defects between the parent and fragment ions. 2.1.1.1 Cadambine‑Type Alkaloids Peak 21 was identified as cadambine from the [M+H]+ ion at m/z 545.2129 with the diagnostic MS2 ions at m/z 383.1612 (C21H22N2O5) and 351.1245 (C20H18N2O4), corresponding to the sequential loss of glycosyl and MeOH moieties [18]. Peak 19 showed the loss of 17 Da from 565 to 548, and the loss of 162 Da from 548 to 386, which was characteristic for the hydrated derivat (...truncated)