Epidemiological evidence suggests that flavonoids may play an important role in the decreased risk of chronic diseases associated with a diet rich in plant-derived foods. Flavonoids are also common constituents of plants used in traditional medicine to treat a wide range of diseases. The purpose of this article is to summarize the distribution and biological activities of one of the most common flavonoids: luteolin. This flavonoid and its glycosides are widely distributed in the plant kingdom; they are present in many plant families and have been identified in Bryophyta, Pteridophyta, Pinophyta and Magnoliophyta. Dietary sources of luteolin include, for instance, carrots, peppers, celery, olive oil, peppermint, thyme, rosemary and oregano. Preclinical studies have shown that this flavone possesses a variety of pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial and anticancer activities. The ability of luteolin to inhibit angiogenesis, to induce apoptosis, to prevent carcinogenesis in animal models, to reduce tumor growth in vivo and to sensitize tumor cells to the cytotoxic effects of some anticancer drugs suggests that this flavonoid has cancer chemopreventive and chemotherapeutic potential. Modulation of ROS levels, inhibition of topoisomerases I and II, reduction of NF-kappaB and AP-1 activity, stabilization of p53, and inhibition of PI3K, STAT3, IGF1R and HER2 are possible mechanisms involved in the biological activities of luteolin.

Distribution and biological activities of the flavonoid luteolin.

In this paper, oleuropein and some other related phenolic compounds are reviewed. Their occurrence, distribution, biosynthesis and transformation during maturation and during industrial processing (preparation of table olives and oil production) are described. Their role in human health is proposed based on current human, animal and in vitro studies as molecules with antioxidant and antimicrobial properties.

Oleuropein and related compounds

Lonicera japonica Thunb.: ethnopharmacology, phytochemistry and pharmacology of an important traditional Chinese medicine.

There is growing interest in the elucidation of the biological functions of triterpenoids, ubiquitously distributed throughout the plant kingdom, some of which are used as anticancer and anti-inflammatory agents in Asian countries. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid, is the major component of some traditional medicine herbs and is well known to possess a wide range of biological functions, such as antioxidative, anti-inflammation, and anticancer activities, that are able to counteract endogenous and exogenous biological stimuli. In contrast to these beneficial properties, some laboratory studies have recently revealed that the effects of UA on normal cells and tissues are occasionally pro-inflammatory. Thus, UA may be designated as a double-edged sword with both positive and negative effects, and further evaluations of the effects of UA on the biological status of target cells or tissues are necessary. This review summarizes previous and current information regarding UA, and provides new insights into the underlying molecular mechanisms of its activities.

Ursolic acid : An anti-and pro-inflammatory triterpenoid

Flavonoids and their glycosides, including anthocyanins

Four enantiomerically pure new α-tetralones, (4S)- and (4R)-5-hydroxy-4-methoxy-α-tetralones and (4S)- and (4R)-5,8-dihydroxy-4-methoxy-α-tetralones were isolated, together with five known ones, (4S)- and (4R)-4,8-dihydroxy-α-tetralones, (4S)-4,8-dihydroxy-5-methoxy-α-tetralone and (4S)- and (4R)-4-hydroxy-α-tetralones, from the fruit of Juglans mandshurica MAXIM. var. sieboldiana MAKINO. Their structures were established on the basis of spectral analysis. To the best of our knowledge, this is the first isolation of the (4R)-4-hydroxy-α-tetralone derivative from Juglans species.

Studies on the Constituents of Juglans Species. I. Structural Determination of (4S)- and (4R)-4-Hydroxy-α-tetralone Derivatives from the Fruit of Juglans mandshurica M AXIM. var. sieboldiana M AKINO

Secoiridoid glycosides from the flower buds of Lonicera japonica

From the peels of Citrus hassaku HORT. ex TANAKA (Rutaceae), eight flavonoid aglycones were isolated and characterized as 4', 5, 6, 7, 8-pentamethoxyflavone (I), 3', 4', 5, 6, 7, 8-hexamethoxyflavone (II), 3, 3', 4', 5, 6, 7, 8-heptamethoxyflavone (III), 3', 4', 5, 6, 7-pentamethoxyflavone (IV), 4', 5, 7-trimethoxyflavone (V), 3, 3', 4, ', 5, 7, 8-hexamethoxyflavone (VI), 4', 5, 7, 8-tetramethoxyflavone (VII) and 3', 4', 5, 7, 8-pentamethoxyflavone (VIII), based on spectral and chemical data.

On the Flavonoid constituents from the Peels of Citrus hassaku HORT. ex TANAKA

Norisoprenoids from Viburnum dilatatum

Four edible mushrooms, Panellus serotinus, Lepista nuda, Tricholoma matsutake and Naematoloma sublateritium, have been investigated chemically. Two new sterols, 5α, 9α-epidioxy-(22E)-ergosta-7, 22-diene-3β, 6α-diol (1) and 5α, 9α-epidioxy-(22E)-ergosta-7, 22-diene-3β, 6β-diol (2), have been isolated from Panellus serotinus. Compound 2 was also isolated from Lepista nuda. A new sterol, 3β, 5α, 9α, 14β-tetrahydroxy-(22E)-ergosta-7, 22-dien-6-one (3), and compound 2 have been isolated from Tricholoma matsutake. Three new triterpenoids, sublateriols A-C (4-6), have been isolated from Naematoloma sublateritium. The structures of the new compounds were elucidated on the basis of their spectral data.

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Koichi Machida

Papers

Studies on the Constituents of Juglans Species. I. Structural Determination of (4S)- and (4R)-4-Hydroxy-α-tetralone Derivatives from the Fruit of Juglans mandshurica M AXIM. var. sieboldiana M AKINO

Secoiridoid glycosides from the flower buds of Lonicera japonica

On the Flavonoid constituents from the Peels of Citrus hassaku HORT. ex TANAKA

Norisoprenoids from Viburnum dilatatum

New sterols and triterpenoids from four edible mushrooms.