Molecules 2019, 24, 1386
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Phillipsburg, NJ, USA). The marigold oleoresin was purchased from Oleo-especias (Zapopan, Jalisco,
Mexico). For the extraction of lutein esters, the marigold oleoresin (100 g) was washed successively
with 50 mL of isopropyl alcohol and 50 mL of hexane. Each washing process was repeated three times.
Then, the final residue was dried at room temperature, giving 65 g of dry starting material enriched in
lutein esters.
3.2. Free (3R,3’R,6’R)-Lutein (1) from Oleoresin
The marigold oleoresin (100 g) was hydrolyzed with KOH (11.2 g) in ethanol (EtOH) (125 mL)
under reflux for 3 hours. Upon completion of the reaction, the mixture was neutralized with 10.7%
aqueous H3PO4 (v/v) and washed with 100 mL of hexane. About 12.5 g of a dry orange-red solid was
recovered and purified by precipitation by solvent exchange from dichloromethane to cold methanol.
1
The compound obtained was identified as (3R,3’R,6’R)-lutein (
1
): H-NMR (500 MHz, CDCl3)
δ
(ppm)
(Figure S6): 0.85 (3H, s, H-16’), 1.00 (3H, s, H-17’), 1.07 (6H, s, H16 and H-17), 1.36 (1H, dd, J = 13.1,
7.0 Hz, H-2’A), 1.48 (1H, t, J = 12.0 Hz, H-2A), 1.63 (3H, s, H-18’), 1.74 (3H, s, H-18), 1.78 (1H, m, H-2),
1.84 (1H, dd, J = 13.1, 7.0 Hz, H-2’B), 1.91 (3H, s, H-19’), 1.97 (9H, s, H-19, H-20, and H-20’), 2.05 (1H,
dd, J = 16.5, 9.5 Hz, H-4A), 2.39 (1H, m, H-4B), 2.41 (1H, d, J = 8.1 Hz, H-6’), 4.01 (1H, m, H-3), 4.25
(1H, s, H-3’), 5.44 (1H, dd, J = 15.5, 10.0 Hz, H-7’), 5.55 (1H, s, H-4’), 6.12 (3H, m, H-7, H-8, and H-8’),
6.15 (2H, m, H-10 and H-10’), 6.24 (1H, m, H-14), 6.26 (1H, m, H-14’), 6.35 (1H, m, H-12), 6.37 (1H,
m, H-12’), 6.64 (4H, m, H-11, H-11’, H-15, and H-15’). 13C-NMR (125 MHz, CDCl3)
δ (ppm) (Figure
S7): 12.8 (C-20 and C-20’), 13.1 (C-19 and C-19’), 21.4 (C-18), 22.9 (C-18’), 24.3 (C-17’), 28.7 (C-17), 29.5
(C-16’), 30.3 (C-16), 34.0 (C-1’), 37.1 (C-1), 42.6 (C-4), 44.7 (C-2), 48.4 (C-2’), 54.9 (C-6’), 65.1 (C-3), 65.9
(C-3’), 124.5 (C-4’), 124.8 (C-11’), 124.9 (C-11), 125.6 (C-7), 126.2 (C-5), 128.7 (C-7’), 130.0 (C-15), 130.1
(C-15’), 130.8 (C-10), 131.3 (C-10’), 132.6 (C-14 and C-14’), 135.1 (C-9), 135.7 (C-9’), 136.4 (C-13’), 136.5
(C-13), 137.6 (C-12), 137.7 (C-12’), 137. 8 (C-5’), 138.0 (C-6), 138.5 (C-8 and C-8’). These data match
those published by Otaka et al. [41].
3.3. Synthesis of (3R,3’S)-Zeaxanthin (2)
To 1 mmol (569 mg) of 1 in 10 ml of n-butanol, 561 mg of KOH was added, and the solution was
heated for 12 h at 115 ◦C with vigorous stirring. The reaction was monitored by HPLC. Once 90% of
the conversion was reached, the reaction was stopped by adding 2N of H3PO4 until it resulted in a
neutral pH. A slight excess of water was added; then, the reaction mixture was filtered, and solvent
was removed by rotary evaporation until dry to give a crude residue (540 mg). The compound was
recrystallized using methanol, affording orange crystals (yield 92%). This compound was identified
1
as (3R,3’S)-zeaxanthin (
2
): H-NMR (500 MHz, CDCl3)
δ
(ppm) (Figure S8): 1.07 (12H, s, H-16, H-16’,
H-17, and H-17’), 1.48 (2H, t, J = 12.0 Hz, H-2A), 1.74 (6H, s, H-18 and H-18’), 1.77 (2H, m, H-2B), 1.97
(12H, s, H-19, H-19’, H-20, and H-20’), 2.04 (2H, dd, J = 16.5, 5.0 Hz, H-4A), 2.39 (2H, dd, J = 16.5, 5.0
Hz, H-4B), 4.00 (2H, m, H-3 and H-3’), 6.12 (2H, m, H-7 and H-7’), 6.15 (2H, m, H-8 and H-8’), 6.17 (2H,
m, H-10 and H-10’), 6.26 (2H, m, H-14 and H-14’), 6.37 (2H, d, J = 14.5 Hz, H-12 and H-12’), 6.62 (2H,
m, H-15 and H-15’), 6.64 (2H, m, H-11 and H-11’). 13C-NMR (125 MHz, CDCl3)
δ (ppm) (Figure S9):
12.8 (C-20 and C-20’), (C-19 and C-19’), 21.6 (C-18 and C-18’), 28.7 (C-16 and C-16’), 30.3 (C-17 and
C-17’), 37.1 (C-1 and C-1’), 42.6 (C-4 and C-4’), 48.4 (C-2 and C-2’), 65.1 (C-3 and C-3’), 124.9 (C-11 and
C-11’), 125.6 (C-7 and C-7’), 126.2 (C-5 and C-5’), 130.1 (C-15 and C-15’), 131.3 (C-10 and C-10’), 132.6
(C-14 and C-14’), 135.7 (C-9 and C-9’), 136.4 (C-13 and C-13’), 137.6 (C-12 and C-12’), 137. 8 (C-6 and
C-6’), 138.6 (C-8 and C-8’) [42].
3.4. Synthesis of (3R,3’S)-astaxanthin (3)
Compound
2 (285 mg) was dissolved in methylene chloride (15 mL) and 2.5 mg of iodine was
added. The mixture was stirred for 30 min. The oxidant solution was independently prepared
according to the following procedure: 100 mg of NaBrO3 were dissolved in 5 mL of water and 50
mg of NaHCO3 was added; independently, 56 mg of Na2S2O5 was dissolved in 2 mL of water. Both