Dietary supplementation with purified citrus limonin glucoside does not alter ex vivo functions of circulating T lymphocytes or monocytes in overweight/obese human adults.

Overweight/obesity is associated with chronic inflammation and impairs both innate and adaptive immune responses. Limonoids found in citrus fruits decreased cell proliferation and inflammation in animal studies. We hypothesized that limonin glucoside (LG) supplementation in vivo will decrease the ex vivo proliferation of T cells and the production of inflammatory cytokines by monocytes and T cells.

Citrus limonoids: analysis, bioactivity, and biomedical prospects.

Limonoids are a prominent group of secondary metabolites in citrus fruit. The bitter character of some compounds in this group has historically compromised the quality of citrus fruit and juice. Detecting bitter limonoids in citrus, understanding their origins, and developing methods for their removal from citrus juices have provided the basis for citrus limonoid research.

Evaluation of the antioxidant capacity of limonin, nomilin, and limonin glucoside.

The antioxidant capacity (AOC) of three representative citrus limonoids, limonin, nomilin, and limonin glucoside, was examined by the oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), beta-carotene-linoleic acid bleaching, and 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assays. Pure compounds and proper negative (cinnamic acid) and positive (2,6-di-tert-butyl-4-methylphenol (BHT) and ascorbic acid) controls were used to remove any ambiguity in interpreting results. In all cases, limonin and nomilin gave results equivalent to those of cinnamic acid, indicating that they do not possess any inherent AOC and should not be considered antioxidants.

Determination of limonoate and nomilinoate A-ring lactones in citrus juices by liquid chromatography-electrospray ionization mass spectrometry.

The development of delayed bitterness in citrus products is a major problem to citrus producers and juice processors worldwide. A rapid and sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed to quantify the recognized precursors of limonoid derived delayed bitterness, limonoate and nomilinoate A-ring lactones, in a wide variety of citrus juices. The limonoid A-ring lactones were isolated by solid-phase extraction from juice samples, analyzed by negative ion LC-ESI-MS and quantified utilizing the standard addition method.

Identifying citrus limonoid aglycones by HPLC-EI/MS and HPLC-APCI/MS techniques.

HPLC coupled with normal phase electron ionisation (EI) and atmospheric pressure chemical ionisation (APCI)/ mass spectrometry methods has been applied to identify 17 known neutral limonoid aglycones from Citrus sources. The HPLC-MS data from the known limonoids provided chromatographic characteristics, APCI-derived molecular weight data and EI fragmentation data for each limonoid. EI fragmentation patterns for the limonoids were correlated with structural characteristics.