Table 3.

Amounts of MTX4 present in crude extract from approximately 2.2 million cells of G. excentricus VGO791 and VGO792 and the amounts of toxin remaining after the subsequent liquid-liquid partitioning and LH-20 chromatography purification steps. The MTX4 estimates were obtained using multiple reactions monitoring (MRM) mode on LC-LRMS/MS. Quantification of MTX4 was based on the MRM transition 1646.2 → 1646.2 m/z ([M − 2H]²⁻ → [M − 2H]²⁻) using MTX as the reference standard, quantified using the MRM transition 1689.8 → 1689.8 m/z ([M − 2H]²⁻ → [M − 2H]²⁻). Amounts of MTX4 were therefore expressed in µg MTX eq, assuming an equimolar response of MTX4 and MTX in MS. * MSF: aqueous methanol soluble fraction.

Strain Name	Sample Name	MTX4 (µg MTX eq)	% Recovery (Liquid-Liquid Partitioning)	% Recovery (LH-20)
Gambierdiscus excentricus VGO791	Crude extract	160.1	100%
	Liquid-liquid partitioning of crude extract
	MSF *	137.4	85.8%
	Size-exclusion chromatography (LH-20) of MSF sample
	Ve = 12.5–15.0 mL	19.1		13.9%
	Ve = 15.0–17.5 mL	69.2		50.4%
	Ve = 17.5–20.0 mL	19.0		13.8%
	Ve = 20.0–22.5 mL	4.5		3.3%
	Ve = 22.5–25.0 mL	1.5		1.1%
	Ve = 25.0–27.5 mL	1.2		0.9%
Gambierdiscus excentricus VGO792	Crude extract	43.1	100%
	Liquid-liquid partitioning of crude extract
	MSF *	34.2	79.4%
	Size-exclusion chromatography (LH-20) of MSF sample
	Ve = 13.0–14.0 mL	0.6		1.7%
	Ve = 14.0–15.0 mL	4.6		13.5%
	Ve = 15.0–16.0 mL	10.3		30.1%
	Ve = 16.0–17.0 mL	6.2		18.0%
	Ve = 17.0–18.0 mL	3.3		9.6%
	Ve = 18.0–19.0 mL	1.8		5.3%
	Ve = 19.0–20.0 mL	1.2		3.4%
	Ve = 20.0–21.0 mL	0.8		2.5%
	Ve = 21.0–22.0 mL	0.6		1.9%
	Ve = 22.0–23.0 mL	0.6		1.7%
	Ve = 23.0–24.0 mL	<LOQ
	Ve = 24.0–25.0 mL	<LOQ
	Ve = 25.0–26.0 mL	<LOQ