Hydrophilic Carotenoids: Carotenoid Aggregates - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 50

8

6

4

2

0

210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

-2

-4

-6

λ (nm)

FIGURE 3.12 CD spectrum of ( S , S )-astaxanthin 3.6 in MeOH (—), ( S , S )-astaxanthin dioxime hydrochlo-
ride 3.38 in MeOH (- - -) and of aggregates of 3.38 in water (—). (Willibald, J. et al., Chem. Phys. Lipids , 161,
32, 2009. With permission.)

3.6 AGGREGATE STABILITY
Self-aggregation of carotenoids is synonymous with self-stabilization. The aggregates of the phos-
pholipid, 3.15 , and Cardax, 3.19 , are thermostable at T

50°C, Figure 3.13, whereas the aggregates
of zeaxanthin, 3.3 , and lutein, 3.4 , are disrupted at 45°C and 55°C, respectively (Douillard et al.
1983). Carotenoid aggregates withstand much longer rel uxing in MeOH/HCl than the nonaggre-
gated monomolecular solution before bleaching occurs (Sliwka et al. 2007). Astonishingly, although
the aggregate membrane is transparent, carotenoid aggregate dispersions resist light irradiation for
a substantially longer time than a nonaggregated monomolecular solution (Lüddecke et al. 1999).

≥

1.0

T , ºC

0.8

15
20
25
30
35
40
45
50

0.6

0.4

0.2

0.0

300 400 500 600 700

λ (nm)

FIGURE 3.13 Thermostability of H -aggregates of Cardax 3.19 in water. (From Melø, T.B., Trondheim,
unpublished.)