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The contents of phenolic compounds, protein precipitation capacity (PPC) and in vitro gas production of tropical browse species were evaluated. The stoichiometric relationship between in vitro gas measured on incubation of tannin-containing browses in buffered rumen fluid and calculated from short chain fatty acid (SCFA) production was investigated. Crude protein (CP) contents in the browses ranged from 54 to 300 g/kg dry matter (DM). Total phenol (TP), tannins (T) and condensed tannins (TP and T as tannic acid equivalent; CT, as leucocyanidin equivalent) ranged from 17–250, 7–214, and 0–260 g/kg DM respectively, and PPC from 0 to 1066 μg BSA precipitated/g DM. CP content of browses was negatively correlated with TP, T, CT and PPC. A significant correlation was observed between per cent change in gas production on addition of polyethylene glycol (PEG) and the contents of phenolics (r = 0.76 for both TP and T). Addition of PEG to tannin-containing browses increased in vitro gas production. PPC was significantly correlated with TP (r = 0.87; P<0.001), T (r = 0.83; P<0.001), and CT (r = 0.41; P<0.05). A good relationship (R2 = 0.94; P<0.001) was observed between measured in vitro gas production and that calculated from SCFA. The molar proportions of SCFA were not affected by the inclusion of PEG (P>0.05). The relationship between in vitro gas measured on incubation of browse leaves and that calculated from SCFA allows prediction of SCFA from gas production.

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Lutein is an oxygenated carotenoid (xanthophyll) found in dark green leafy vegetables. High intakes of lutein may lower the risk of age-related macular degeneration. Current understanding of human lutein metabolism as it might occur in vivo is incomplete. Therefore, we conducted a feasibility study where we dosed a normal adult woman with 14C-lutein (125 nmol, 36 nCi 14C), dissolved in olive oil (0.5 g/kg body weight) and mixed in a banana shake. Blood, urine, and feces collected before the dose was administered served to establish baseline values. Thereafter, blood was collected for 63 d following the dose, while feces and urine were collected for 2 wk post-dose. The 14C contents in plasma, urine, and feces were measured by accelerator MS. The 14C first appeared in plasma 1 h after dosing and reached its highest level, approximately2.08% of dose/L plasma, at 14 h post-dose. The plasma pattern of 14C did not include a chylomicrons/VLDL (intestinal) peak like that when the same subject received 14C-beta-carotene (a previous test), suggesting that lutein was handled differently from beta-carotene by plasma lipoproteins. Lutein had an elimination half-life (t1/2) of approximately10 d. Forty-five percent of the dose of 14C was eliminated in feces and 10% in urine in the first 2 d after dosing. Quantifying human lutein metabolism is a fertile area for future research.