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bio- refinery-based bark processing. Keywords: biorefinery; flavanyl units; hardwood bark; inter- flavanoid bonds; linear diarylheptanoids; oregonin; tannins; proantocyanidins; sorbents. Introduction Currently only 6=109 t of the 170=109 t of biomass pro- duced annually by photosynthesis are utilised and only 3% of this is in the non-food application (Kamm and Kamm 2004). However, increased R&D activities are directed toward a sustainable economy based on renewable sources such as plant biomass (Cherubini 2010). In this context, tree barks have a high potential to

Abstract

The lamina, main vein and peduncle anatomical properties of Centaurea sadleriana Janka plants from two populations, were examined using light and scanning electron microscopy. The indumentum was comprised of glandular and non-glandular trichomes of two types. The leaves were amphistomatic, isolateral, with strongly developed palisade tissue. Secretory ducts were observed along the phloem or sclerenchyma of large vascular bundles. Collenchyma alternated with chlorenchyma in the main vein and peduncle. Large groups of strongly lignified sclerenchyma were present along the phloem of peduncle vascular bundles. These features, together with thickened walls of epidermal cells and cuticle, numerous trichomes and thick-walled parenchyma in the perimedullar zone, were perceived as a xeromorphic peduncle structural adaptation. Non-enzymatic antioxidant compounds of phenolic origin were detected in small amounts and their respective content was higher in leaves compared to inflorescences. Compounds of phenolic orgin showed positive correlation with total potenial of antioxidant activity indicated by the DPPH assay. Greater total quantity of polyphenols and tannins was detected in leaves of plants from Zobnatica locality, while leaves of plants from Rimski Sanac were characterized by higher content of total flavonoids and proantocyanidins. Phytochemical analysis showed that dominant secondary biomolecules in inflorescences were phenolic pigments including anthocyanins and leucoanthocyanins, and free quinones in leaves.

SAPWOODS OUTER INNER HEARTWOODS HEARTWOODS Fig. 4. Insoluble proantocyanidins in sapwoods and heartwoods of three different Quercus cerris L. trees (l to 3). External flakes (white bars) and internal flakes (black bars) wjjυ Ά%« 1.0J G W >>ω <ϋ * & «^ <U •H Ό 0.5- ι 1 2 3 4 5 6 SAPWOOD OUTER HEARTWOOD 7 8 9 INNER HEARTWOOD Fig. 5. Total phenols in diethyl ether extracts along a transversal section of Quercus cerris L. wood. Dried at room temperature (white bars); dried at 140 °C (black bars); numbers l to 9 refer to Position of samples (see Fig. 1) Discussion The

- propagated plants [(4.07 ð 0.38)%] (p 0.05). Fig. 4. Total proanthocyanidin content of Cecropia glaz- iovi leaves collected from native, cultivated and micro- propagated (clone) plants during the dry season. NYL, native young leaves; NML, native mature leaves; CTYL, cultivated young leaves; CTML, cultivated mature leaves; CLYL, micropropagated (clone) young leaves; CLML, micropropagated (clone) mature leaves. Fig. 5. Total proantocyanidin content of Cecropia glazi- ovi leaves collected from native, cultivated and micro- propagated (clone) plants during the rainy season

, high-resolution transmission electron microscope (HR-TEM), and EDX [ 38 ]. The study concluded that polyphenolic compounds such as catechin, epicatechin, anthocyanidin, proantocyanidin, and condensed tannins abundantly present in the grape wastes could be responsible for the formation of AuNPs. Furthermore, Patra and Baek [ 70 ] used aqueous extract of watermelon rind for the synthesis of AuNPs, which were spherical in shape and 20–140 nm in size and absorbed maximally at 560 nm. The synthesized particles facilitated by the catalytic action of phenolic compounds

(catechin) units are join- ed by C4-C8 or C4-C6 linkages (Porter 1974; Hemingway, McGraw 1976). Di- and triflavanols with a similar structure were also isolated from the inner bark of sugi (Cryptomeria japonica) (Samejima, Yoshimoto 1979) (Fig. 9-8). Samejima and Yoshimoto (1981) characterized the bark tannins of numerous conifer species by determining the tannin-flavanol ratio (T/F value). According to this study the bark tannins of many conifers consist mainly of proantocyanidins. Fig. 9-8 . Diflavanols and triflavanols as isolated from pine (Pinus radiata) and

in Wood