Flavonoids as natural phenolic compounds and their role in therapeutics: an overview

Background Natural plants and plant-derived formulations have been used by mankind from the ancient period of time. For the past few years, many investigations elaborated the therapeutic potential of various secondary chemicals present in the plants. Literature revealed that the various secondary metabolites, viz. phenolics and flavonoids, are responsible for a variety of therapeutic action in humans. Main body In the present review, an attempt has been made to compile the exploration of natural phenolic compounds with major emphasis on flavonoids and their therapeutic potential too. Interestingly, long-term intake of many dietary foods (rich in phenolics) proved to be protective against the development and management of diabetes, cancer, osteoporosis, cardiovascular diseases and neurodegenerative diseases, etc. Conclusion This review presents an overview of flavonoid compounds to use them as a potential therapeutic alternative in various diseases and disorders. In addition, the present understanding of phenolics and flavonoids will serve as the basis for the next scientific studies.

Tallow tree allocates contrasting secondary chemicals in response to varying environments along elevational gradients

Aims Understanding how tree species regulate multiple types of secondary chemicals along elevational gradients is critical for elucidating the physiological and ecological strategies of plants in response to varying biotic and/or abiotic environments. This study aims to examine how Chinese tallow tree (Triadica sebifera) allocates resources to the production of different secondary chemicals in response to varying environments across elevational gradients. Methods We conducted field surveys of different herbivore feeding guilds and their damage rates on Chinese tallow trees along an elevational gradient in China and measured secondary chemicals (tannins and flavonoids) in damaged and undamaged leaves. Important Findings The odds of a leaf being damaged (chewing or scarring) decreased with elevation. Flavonoid concentrations increased with elevation in undamaged leaves but decreased with elevation in damaged leaves, with quercitrin contributing most strongly to this pattern, likely as results of plant responding to changing biotic or abiotic stresses along elevational gradients. Tannin concentrations did not vary with elevation, so undamaged leaves had relatively lower tannin to flavonoid ratios at high elevation than at low elevation. Our study reveals variation in herbivory and contrasting trends in plant secondary metabolism along an elevation gradient and highlights the importance of simultaneously considering multiple types of secondary chemicals in plant physiological and ecological strategies.

How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

Some plants that are dispersed by scatter-hoarding animals appear to have evolved the ability to manipulate the behaviour of those animals to increase the likelihood that seeds and nuts will be stored and that a portion of those items will not be recovered. Plants have achieved this in at least four ways. First, by producing large, nutritious seeds and nuts that are attractive to animals and that stimulate hoarding behaviour. Second, by imposing handling costs that cause animals to hoard rather than to eat items immediately. These handling costs can take one of two forms: physical barriers (e.g. hard seed coats) that take time to remove and secondary chemicals (e.g. tannins) that impose metabolic costs. Third, by masting, where a population of plants synchronizes reproductive effort, producing large nut crops at intervals of several years. Mast crops not only satiate seed predators, but also increase the amount of seed dispersal because scatter-hoarding animals are not easily satiated during caching (causing animals to store more food than they can consume) but are satiated during cache recovery. And fourth, by producing seeds that do not emit strong odours so that buried seeds are less likely to be discovered. These, and perhaps other, traits have increased the relative success of plant species with seeds dispersed by scatter-hoarding animals.

Annona muricata (Graviola): Toxic or Therapeutic

The medicinal plant Annona muricata (Annonaceae), also known as Graviola or Soursop, is reported here to contain imino sugar alkaloids. This is the first report of imino sugars in the Annonaceae. Graviola has very broad medicinal claims and is also widely consumed as a food and in drinks in the tropics. The plant produces a wide range of secondary chemicals, some already known to be toxic, but the discovery here of the imino sugars as a new group of chemicals, including the neurotoxin swainsonine, raises questions about the safety of consumption of this plant.

Secondary chemicals protect mould from fungivory

The vast repertoire of toxic fungal secondary metabolites has long been assumed to have an evolved protective role against fungivory. It still remains elusive, however, whether fungi contain these compounds as an anti-predator adaptation. We demonstrate that loss of secondary metabolites in the soil mould Aspergillus nidulans causes, under the attack of the fungivorous springtail Folsomia candida , a disadvantage to the fungus. Springtails exhibited a distinct preference for feeding on a mutant deleted for LaeA, a global regulator of Aspergillus secondary metabolites. Consumption of the mutant yielded a reproductive advantage to the arthropod but detrimental effects on fungal biomass compared with a wild-type fungus capable of producing the entire arsenal of secondary metabolites. Our results demonstrate that fungal secondary metabolites shape food choice behaviour, can affect population dynamics of fungivores, and suggest that fungivores may provide a selective force favouring secondary metabolites synthesis in fungi.

Edible forage yield and nutritive value of poplar and willow

Poplar and willow on farms are a potential source of supplementary forage during summer. To incorporate poplar and willow into farm feed budgets, a method is needed to non-destructively estimate the edible forage yield of the trees. Also needed is an estimate of the nutritive value of the forage. Previously uncut trees on hill farms in the lower North Island were measured and a relationship between tree forage yield and diameter of the trunk at breast height (DBH, 1.4 m) was developed. The DBH was from 5 to 32 cm and the forage yield from 1 to 66 kg dry matter (DM)/tree. Nutritive value of poplar and willow (metabolisable energy 8-9 MJ/kg DM) was similar to that of normal summer pasture, but was lower in fibre and higher in soluble carbohydrate, and of higher nutritive value than drought pasture. The concentrations of the secondary chemicals condensed tannins and phenolic glycosides were high in poplars and willows, and they have some positive effects on livestock performance, but their role requires further research. It was concluded that poplar and willow provide forage of sufficient quantity and quality to warrant using them as supplements to pasture for feeding to livestock during summer droughts.