Orally administered low-molecular weight agaro-oligosaccharides are absorbed into the plasma of healthy humans.

Agaro-oligosaccharides (AOSs) are known to have biological activities, such as anti-inflammatory, anti-tumor, and anti-obesity effects. Although existing evidence suggests the presence of AOSs in peripheral tissues after oral administration, whether AOSs permeate into the blood circulation remains unknown. Thus, we hypothesized that AOSs with low-molecular weight can permeate the human gastrointestinal tract. To test this hypothesis, the time course of absorption was examined by analyzing plasma samples before and 1, 2, and 4 h after ingestion. Analysis was performed using liquid chromatography/mass spectrometry after labeling with p-aminobenzoic ethyl ester. Our results showed that the plasma concentration of agarobiose (Abi) was higher than that of agarotetraose (Ate); however, agarohexaose was not detected. Additionally, plasma levels of Abi and Ate were proportional to the dose. These results suggest that permeation efficiency is dependent on the molecular weight and that the systemic absorption of Abi via the gastrointestinal tract is better than that of Ate. These findings will contribute to a better understanding of the bioactivity of orally administered AOSs in peripheral tissues.

Intestinal permeability of agaro-oligosaccharides: Transport across Caco-2 cell monolayers and pharmacokinetics in rats.

Agaro-oligosaccharides (AOSs), even-numbered oligosaccharides prepared from agar, are applied to various food, including supplements, drinks, and jellies because of their biological activities. This study aimed to evaluate the AOS permeation in the gastrointestinal tract in vivo and in vitro. Agarobiose (Abi), agarotetraose (Ate), and agarohexaose (Ahe) were detected in rat plasma after oral administration of AOSs. The detection level of agarobiose in the plasma was higher than that of agarohexaose, which was consistent with the permeation study using Caco-2 cell monolayers. Further, the adenosine triphosphate inhibitor (sodium azide) or endocytosis inhibitor (colchicine) did not inhibit AOS permeation through Caco-2 cell monolayers. Conversely, AOS permeation enhanced upon treatment with cytochalasin B, a tight junction disrupter, suggesting that AOSs might have passed mainly through the tight junctions between the intestinal epithelial cells. These results indicate that AOSs, especially agarobiose, can be absorbed as an intact form via the gastrointestinal tract across the intestinal epithelium through the paracellular pathway.

Does the brassinosteroid signal pathway in photomorphogenesis overlap with the gravitropic response caused by auxin?

Brassinosteroid (BR) and auxin co-regulate plant growth in a process termed cross-talking. Based on the assumption that their signal transductions are partially shared, inhibitory chemicals for both signal transductions were screened from a commercially available library. A chemical designated as NJ15 (ethyl 2-[5-(3,5-dichlorophenyl)-1,2,3,4-tetrazole-2-yl]acetate) diminished the growth promotion of both adzuki bean epicotyls and Arabidopsis seedlings, by the application of either BR or auxin. To understand its target site(s), bioassays with a high dependence on the signal transduction of either BR (BR-signaling) or auxin (AX-signaling) were performed. NJ15 inhibited the photomorphogenesis of Arabidopsis seedlings grown in the dark, which mainly depends on BR-signaling, while NJ15 also inhibited their gravitropic responses mainly depending on AX-signaling. On the study for the structure-activity relationships of NJ15 analogs, they showed strong correlations on the inhibitory profiles between BR- and AX-signalings. These correlations imply that NJ15 targets the downstream pathway after the integration of BR- and AX-signals.