Department of Chemistry, Villanova University, Villanova, PA, 19085, USA.
Department of Chemistry, Villanova University, Villanova, PA, 19085, USA; Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine at the University of Pennsylvania, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA.
Phytochemistry. 2021 May;185:112662. doi: 10.1016/j.phytochem.2021.112662. Epub 2021 Mar 27.
Apocynaceae are well known for diverse specialized metabolites that are distributed in a phylogenetically informative manner. Pyrrolizidine alkaloids (PAs) have been reported sporadically in one lineage in the family, the APSA clade, but few species have been studied to date. We conducted the first systematic survey of Apocynaceae for retronecine-type PAs, sampling leaves from 231 species from 13 of 16 major lineages within the APSA clade using HPLC-MS/MS. We also followed up preliminary evidence for infra-specific variation of PA detectability in Echites umbellatus Jacq. Four precursor ion scans (PREC) were developed for a high-throughput survey for chemicals containing a structural moiety common to many PAs, the retronecine core. We identified with high confidence PAs in 7 of 8 sampled genera of tribe Echiteae, but not in samples from the closely related Odontadenieae and Mesechiteae, confirming the utility of PAs as a taxonomic character in tribal delimitation. Occurrence of PAs in Malouetieae is reported with moderate confidence in Galactophora schomburgkiana Woodson and Eucorymbia alba Stapf, but currently we have low confidence of their presence in Holarrena pubescens Wall. ex G. Don (the one Malouetieae species where they were previously reported), as well as in Holarrena curtisii King & Gamble and in Kibatalia macrophylla (Pierre ex Hua) Woodson. Candidate PAs in some species of Wrightia R. Br. (Wrightieae) and Marsdenia R. Br. (Marsdenieae) are proposed with moderate confidence, but a subset of the compounds in these taxa presenting with a PA-like fragmentation pattern are more likely to be aminobenzoyl glycosides. Candidate PAs are reported in species with predicted (VXXXD) and unexpected (IXXXN) amino acid motifs in their homospermidine synthase-like genes. Detectability of PAs varies among samples of Echites umbellatus and intra-individual plasticity contributes to this variation. Of toxicological importance, novel potential sources of human exposure to pro-toxic PAs were identified in the medicinal plant, Wrightia tinctoria R.Br., and the food plants, Marsdenia glabra Cost. and Echites panduratus A. DC., warranting immediate further research to elucidate the structures of the candidate PAs identified. Method development and limitations are discussed.
夹竹桃科以其分布在系统发生上具有信息意义的各种特殊代谢产物而闻名。吡咯里西啶生物碱（PAs）曾在该科的一个谱系，APSA 分支中零星报道过，但迄今为止，只有少数物种进行了研究。我们使用 HPLC-MS/MS 对 APSA 分支中 16 个主要谱系中的 13 个谱系中的 231 种植物的叶子进行了夹竹桃科中首次对 retronecine 型 PAs 的系统调查。我们还对 Echites umbellatus Jacq. 的 PA 可检测性的种内变异的初步证据进行了跟进。我们开发了四个前体离子扫描（PREC），用于高通量调查含有许多 PA 共同结构部分的化学物质，即 retronecine 核心。我们在 8 个取样的 Echiteae 族属中 7 个属中高度置信地鉴定了 PAs，但在密切相关的 Odontadenieae 和 Mesechiteae 中没有鉴定到 PAs，这证实了 PAs 在族界定中的分类学特征的有用性。Galactophora schomburgkiana Woodson 和 Eucorymbia alba Stapf 中中等置信度报告了 Malouetieae 中的 PAs 存在，但目前我们对 Holarrena pubescens Wall. ex G. Don（先前报告的 Malouetieae 物种之一）以及 Holarrena curtisii King & Gamble 和 Kibatalia macrophylla (Pierre ex Hua) Woodson 中 PAs 的存在的置信度较低。Wrightia R. Br.（Wrightieae）和 Marsdenia R. Br.（Marsdenieae）中某些物种的候选 PAs 是中度置信度提出的，但这些类群中具有 PA 样断裂模式的化合物的一部分更可能是氨基苯甲酰糖苷。在其 homospermidine 合酶样基因中具有预测的（VXXXD）和意外的（IXXXN）氨基酸基序的 Wrightia tinctoria R.Br.和 Marsdenia glabra Cost. 和 Echites panduratus A. DC. 等药用植物和食用植物的物种中报告了候选 PAs，这表明人类接触潜在毒性的 PA 的新潜在来源，这需要立即进行进一步研究以阐明鉴定出的候选 PA 的结构。讨论了方法的开发和局限性。
