Wrightieae, R. Br.

Barny, Lea A., Tasca, Julia A., Sanchez, Hugo A., Smith, Chelsea R., Koptur, Suzanne, Livshultz, Tatyana & Minbiole, Kevin P. C., 2021, Chemotaxonomic investigation of Apocynaceae for retronecine-type pyrrolizidine alkaloids using HPLC-MS / MS, Phytochemistry (112662) 185, pp. 1-15 : 5-8

2.4. Wrightieae

Wrightieae are sister to the rest of the APSA clade and include three genera ( Livshultz et al., 2007). Potential PAs were detected in leaves of 5 of 11 species of Wrightia R.Br. and in seeds of Wrightia tinctoria ( Table 2) but none of the three species of Pleioceras Baill. and Stephanostema K. Schum sampled ( Table S2). The most frequent candidate ions had m/z 432.3–432.5, containing both m/z 120 and 138 fragments. These compounds have a similar mass to a modified glycoside, 2-aminobenzoyl O-β- D-apiofuranosyl-(1 → 6)-β- D-glucopyranoside (MW = 431.4), from W. antidysenterica , that is also predicted to yield m/z 120 and 138 fragments ( Fig. 5 ) ( Srinroch et al., 2019). Thus we consider it unlikely that these compounds are PAs. In W. tinctoria samples, there is coelution with m/z 270.2, 300.2 and 328.3 compounds that appeared with lower abundances (counts per second). These compounds are identified as PAs with moderate confidence based on their fragmentation patterns (m/z 120, 138). Alterations to the chromatography method associated with these scans can increase the resolution of these compounds currently co-eluting within the chromatography, thereby increasing the sensitivity to these ions by diminishing ion suppression. One of these candidate PAs (m/z 300.2) could be a breakdown product of the putative aminobenzoyl glycoside (m/z 432.4) ( Fig. 5 ). The D-apiofuranosyl residue, joined by a beta-1,6 linkage to the D-glucopyranoside, could be lost via insource fragmentation resulting in the appearance of the precursor ion, m/z 432, in addition to a m/z 300 ion in PREC 120 and 138 scans at the same retention time ( Fig. 5 ). A standard of 2-aminobenzoyl O -β -D-apiofuranosyl-(1 → 6)- β -D-glucopyranoside would need to be analyzed on the devised precursor scans to determine if insource fragmentation is a potential cause of the m/z 300 ion in W. tinctoria samples. The benzoxazinoid glycoside, blepharin (MW = 327.3), reported from W. religiosa ( Sahakitpichan et al., 2018) , has a similar mass to another candidate PA from W. tinctoria (m/z 328.3). Blepharin is not predicted to readily yield m/z 120 or 138 compounds under our experimental conditions, but a mass spectrum for the compound, obtained in negative electrospray ionization (ESI-) mode, has low abundance ions at m/z 118 and 136 ( Horai et al., 2010; Tsugawa et al., 2019). Multiple other PREC 120 only ions appeared in these samples including m/z 210.2, 352.1, and 460.0. We suggest with low confidence these molecular ions may be associated with PAs.

Table 2 Samples analyzed on all PREC scans (m/z 120, 138, 156). Samples determined as N: no candidate ions detected, Y (low): low confidence, candidate ions detected only in PREC 120, Y (mod):moderate confidence, candidate ions detected in PREC 120 and PREC 138; Y (low): only candidate ion with mass 432.4–432.5 detected in PREC 120 and PREC 138; Y (high): high confidence, candidate ions detected in PREC 120, 138, and 156. ND: not detected. Vouchers in Table S2.

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Table 2 (continued)

Tribe Species Author sample organ Determination PREC PREC PREC Uncorrected Relative

# 120 138 156 Retention Time (min)

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Previously reported alkaloids from Wrightia species include steroidal (pregnane) alkaloids from Wrightia pubescens subsp. laniti (Blanco) Ngan (syn. Wrightia javanica A.DC. ) ( Kawamoto et al., 2003). This species is sampled here ( Table S2) and determined as PA negative. Three species, W. tinctoria , W. dubia Spreng. , and W. arborea (Dennst.) Mabb. (syn. W. tomentosa Roem. & Schult. ), are used as sources of indigo ( Ngan, 1965), and the indole-containing compounds indigotin and indirubin are known from W. tinctoria , as well as the quinolizidine, tryptanthrin ( Khyade, 2014), the later also reported from W. pubescens R. Br. ( Traxler et al., 2021). Recent studies of W. religiosa , W. antidysenterica , and W. pubescens have identified benzoxazinoids, megastigmane glycosides, indoxyl glycosides, simple aromatic glycosides, flavonoid glycosides, and lignans ( Sahakitpichan et al., 2018; Srinroch et al., 2019; Traxler et al., 2021), but only one compound, the aforementioned aminobenzoyl glycoside ( Srinroch et al., 2019), is predicted to yield m/z 120 and 138 fragments ( Fig. 5 ).

Figures

Fig. 5. Proposed fragmentation scheme for 2-aminobenzoyl O-β-D-apiofuranosyl-(1 → 6)- β-D-glucopyranoside (m/z 432.15 when protonated) in positive ion mode ESI to m/z 300.11, 138.06, and 120.04 fragments.

Tables

Table 2 Samples analyzed on all PREC scans (m/z 120, 138, 156). Samples determined as N: no candidate ions detected, Y (low): low confidence, candidate ions detected only in PREC 120, Y (mod):moderate confidence, candidate ions detected in PREC 120 and PREC 138; Y (low): only candidate ion with mass 432.4–432.5 detected in PREC 120 and PREC 138; Y (high): high confidence, candidate ions detected in PREC 120, 138, and 156. ND: not detected. Vouchers in Table S2. Tribe Species Author sample organ Determination PREC PREC PREC Uncorrected Relative # 120 138 156 Retention Time (min) Vinceae Ochrosia poweri F.M.Bailey 28097 leaf N ND ND ND Rauvolfia balansae (Baill.) Boiteau 28131 leaf N ND ND ND Rauvolfia verticillata (Lour.) Baill. 28099 leaf N ND ND ND Rauvolfia vomitoria Afzel. 28116 leaf N ND ND ND Melodineae Craspidospermum Bojer ex Decne. 630 leaf N ND ND ND verticillatum Wrightieae Wrightia antidysenterica (L.) R. Br. 28422 leaf Y (low) 432.5 a 432.5 ND 11.43 Wrightia dubia (Sims) Spreng. 28418 leaf Y (low) 432.5a 432.5 ND 11.4 Wrightia dubia (Sims) Spreng. 28421 leaf Y (low) 432.5a 432.5 ND 11.39 Wrightia karaketii D.J. Middleton 28451 leaf Y (low) 432.5 a 432.5 ND 11.48 Wrightia tinctoria R.Br. 29370 seed Y (mod) 210.2 ND ND 7.56 328.5 ND ND 9.99 460 ND ND 10.16 300.2 300.2 ND ~10.36 432.4 a 432.4 ND ~10.36 328.5 328.5 ND ~10.36 270.3 270.3 ND ~10.36 352.1 ND ND 11.4 Wrightia tinctoria R.Br. 29371 seed Y (mod) 210.2 ND ND 7.32 328.5 ND ND 9.96 460 ND ND 10.19 300.2 300.2 ND ~10.36 328.5 328.5 ND ~10.36 270.3 270.3 ND ~10.36 432.4 a 432.4 ND ~10.36 352.1 ND ND 11.36 Wrightia versicolor S.T. Blake 28423 leaf Y (mod) 432.4 a 432.4 ND 11.33 300.2 300.2 ND 11.66 Malouetieae Eucorymbia alba Stapf 28111 leaf Y (mod) 238.3 238.3 ND 11.79 354.4 354.4 ND 11.93 396.4 ND ND 12.96 436.5 ND ND 14.72 Eucorymbia alba Stapf 28112 leaf Y (mod) 238.3 238.3 ND 11.798 354.4 354.4 ND 11.932 436.5 ND ND 14.67 Galactophora Woodson 116 leaf Y (mod) 270.4 270.4 ND 9.76 schomburgkiana 238.2 238.2 ND 11.92 Holarrhena pubescens Wall. ex G. Don 231 leaf N ND ND ND Holarrhena pubescens Wall. ex G. Don 233 leaf N ND ND ND Holarrhena pubescens Wall. ex G. Don 234 leaf N ND ND ND Holarrhena pubescens Wall. ex G.Don 29372 seed Y (low) 474.4 ND ND 9.52 498.4 ND ND 9.83 Malouetia calva Markgr. 28965 leaf N ND ND ND Malouetia cestroides Müll.Arg. 28966 leaf N ND ND ND Apocyneae Amphineurion (Roxb.) G. Don 23 leaf Y (low) 320.4 ND ND 15.16 marginatum Amphineurion (Roxb.) G. Don 52 leaf N ND ND ND marginatum Amphineurion (Roxb.) G. Don 270 leaf Y (low) 320.4 ND ND 15.16 marginatum Apocynum cannabinum L. 28918 leaf N ND ND ND Beaumontia murtonii Craib 267 leaf N ND ND ND Beaumontia murtonii Craib 268 leaf N ND ND ND Trachelospermum Nakai 81 leaf N ND ND ND asiaticum Vallaris solanacea (Roth) O. Kuntze 90 leaf N ND ND ND Odontadenieae Pentalinon luteum (L.) B.F.Hansen & 28673 leaf N ND ND ND Wunderlin Pentalinon luteum (L.) B.F.Hansen & 28676 leaf N ND ND ND Wunderlin Mesechiteae Mandevilla boliviensis (Hook. f.) Woodson 76 leaf Y (low) 444.2 ND ND 9.76 458.5 ND ND 9.96 Echiteae Bahiella infundibuliflora J.F.Morales 28143 leaf Y (high) 300.1 300.1 300.1 10.22 Echites panduratus A. DC. 28459 leaf N ND ND ND Echites umbellatus Jacq. 28516 leaf Y (high) 318.4 318.4 318.4 10.43 300.5 300.5 300.5 10.73 456.2 456.2 456.2 11.93 470.5 470.5 470.5 12.57 444.4 444.4 444.4 12.73 458.3 458.3 ND 12.87 (continued on next page)

Tribe	Species	Author	sample	organ	Determination	PREC	PREC	PREC	Uncorrected Relative
			#			120	138	156	Retention Time (min)
Vinceae	Ochrosia poweri	F.M.Bailey	28097	leaf	N	ND	ND	ND
	Rauvolfia balansae	(Baill.) Boiteau	28131	leaf	N	ND	ND	ND
	Rauvolfia verticillata	(Lour.) Baill.	28099	leaf	N	ND	ND	ND
	Rauvolfia vomitoria	Afzel.	28116	leaf	N	ND	ND	ND
Melodineae	Craspidospermum	Bojer ex Decne.	630	leaf	N	ND	ND	ND
	verticillatum
Wrightieae	Wrightia antidysenterica	(L.) R. Br.	28422	leaf	Y (low)	432.5 a	432.5	ND	11.43
	Wrightia dubia	(Sims) Spreng.	28418	leaf	Y (low)	432.5 a	432.5	ND	11.4
	Wrightia dubia	(Sims) Spreng.	28421	leaf	Y (low)	432.5 a	432.5	ND	11.39
	Wrightia karaketii	D.J. Middleton	28451	leaf	Y (low)	432.5 a	432.5	ND	11.48
	Wrightia tinctoria	R.Br.	29370	seed	Y (mod)	210.2	ND	ND	7.56
						328.5	ND	ND	9.99
						460	ND	ND	10.16
						300.2	300.2	ND	~10.36
						432.4 a	432.4	ND	~10.36
						328.5	328.5	ND	~10.36
						270.3	270.3	ND	~10.36
						352.1	ND	ND	11.4
	Wrightia tinctoria	R.Br.	29371	seed	Y (mod)	210.2	ND	ND	7.32
						328.5	ND	ND	9.96
						460	ND	ND	10.19
						300.2	300.2	ND	~10.36
						328.5	328.5	ND	~10.36
						270.3	270.3	ND	~10.36
						432.4 a	432.4	ND	~10.36
						352.1	ND	ND	11.36
	Wrightia versicolor	S.T. Blake	28423	leaf	Y (mod)	432.4 a	432.4	ND	11.33
						300.2	300.2	ND	11.66
Malouetieae	Eucorymbia alba	Stapf	28111	leaf	Y (mod)	238.3	238.3	ND	11.79
						354.4	354.4	ND	11.93
						396.4	ND	ND	12.96
						436.5	ND	ND	14.72
	Eucorymbia alba	Stapf	28112	leaf	Y (mod)	238.3	238.3	ND	11.798
						354.4	354.4	ND	11.932
						436.5	ND	ND	14.67
	Galactophora	Woodson	116	leaf	Y (mod)	270.4	270.4	ND	9.76
schomburgkiana
						238.2	238.2	ND	11.92
	Holarrhena pubescens	Wall. ex G. Don	231	leaf	N	ND	ND	ND
	Holarrhena pubescens	Wall. ex G. Don	233	leaf	N	ND	ND	ND
	Holarrhena pubescens	Wall. ex G. Don	234	leaf	N	ND	ND	ND
	Holarrhena pubescens	Wall. ex G.Don	29372	seed	Y (low)	474.4	ND	ND	9.52
						498.4	ND	ND	9.83
	Malouetia calva	Markgr.	28965	leaf	N	ND	ND	ND
	Malouetia cestroides	Müll.Arg.	28966	leaf	N	ND	ND	ND
Apocyneae	Amphineurion	(Roxb.) G. Don	23	leaf	Y (low)	320.4	ND	ND	15.16
marginatum
	Amphineurion	(Roxb.) G. Don	52	leaf	N	ND	ND	ND
marginatum
	Amphineurion	(Roxb.) G. Don	270	leaf	Y (low)	320.4	ND	ND	15.16
marginatum
	Apocynum cannabinum	L.	28918	leaf	N	ND	ND	ND
	Beaumontia murtonii	Craib	267	leaf	N	ND	ND	ND
	Beaumontia murtonii	Craib	268	leaf	N	ND	ND	ND
	Trachelospermum	Nakai	81	leaf	N	ND	ND	ND
asiaticum
	Vallaris solanacea	(Roth) O. Kuntze	90	leaf	N	ND	ND	ND
Odontadenieae	Pentalinon luteum	(L.) B.F.Hansen &	28673	leaf	N	ND	ND	ND
		Wunderlin
	Pentalinon luteum	(L.) B.F.Hansen &	28676	leaf	N	ND	ND	ND
		Wunderlin
Mesechiteae	Mandevilla boliviensis	(Hook. f.) Woodson	76	leaf	Y (low)	444.2	ND	ND	9.76
						458.5	ND	ND	9.96
Echiteae	Bahiella infundibuliflora	J.F.Morales	28143	leaf	Y (high)	300.1	300.1	300.1	10.22
	Echites panduratus	A. DC.	28459	leaf	N	ND	ND	ND
	Echites umbellatus	Jacq.	28516	leaf	Y (high)	318.4	318.4	318.4	10.43
						300.5	300.5	300.5	10.73
						456.2	456.2	456.2	11.93
						470.5	470.5	470.5	12.57
						444.4	444.4	444.4	12.73
						458.3	458.3	ND	12.87