Hieracium / Havikskruid

In grazige bermen en op andere grazige plekken vallen de oranje tot rood gekleurde hoofdjes van Oranje havikskruid, Hieracium aurantiacum, direct op. Deze planten uit de Composietenfamilie zijn sterk behaard, maar hebben geen donzig zilverwitte beharing aan de onderzijde van de bladeren. Aan de bloeistengel zitten de hoofdjes zeer dicht bij elkaar; pas wanneer er meerdere hoofdjes in bloei staan vormt zich een schermvormige bloeiwijze.

Havikskruiden kunnen ook ongeslachtelijke tot bevruchting komen. We noemen dat een apomictische voortplanting. In het vruchtbeginsel wordt dan alleen DNA afkomstig van dezelfde plant bij elkaar gevoegd. Het zal duidelijk zijn dat in dit geval de dochterplant volstrekt het zelfde genoom heeft als de moederplant. Het is een natuurlijke vorm van kloneren. 

Alleen de Hieracium pilosella wordt medicinaal gebruikt. 
 Biological activity of new flavonoid from Hieracium pilosella L.
Monika Gawrońska-Grzywacz, Tadeusz Krzaczek, Renata Nowak, Renata Los, Anna Malm, Małgorzata Cyranka, Wojciech Rzeski
Hieracium pilosella L. (Asteraceae) is a well-known plant used in ethno-medicine as its inflorescences are particularly rich in beneficial polyphenolics. This research aimed to elucidate the structure of a new flavone glycoside isolated from the inflorescences of Hieracium pilosella and evaluate its antioxidant, antimicrobial and antiproliferative activities. The chromatographic methods were successfully applied to isolate the new flavonoid. Its structure was determined by subsequent UV, NMR and MS experiments and identified as isoetin 4′-O-β-D-glucopyranoside. Free radical scavenging capacity was examined by measuring the scavenging activity of the new isoetin derivative on 2,2-diphenyl-1-picrylhydrazyl (DPPH). The compound was also screened for spectrum of antimicrobial activity using the agar well diffusion method. Minimum inhibitory concentration (MIC) for Pseudomonas aeruginosa ATCC 9027 was performed by the micro-dilution broth method. The antiproliferative effect of tested glycoside was assessed in two human tumor cell lines derived from lung (A549) and colon (HT-29) carcinoma and cell proliferation was determined by means of MTT method. The tested compound showed high antiradical activity, reducing the DPPH? with EC50 7.9 μM (3.7 µg/ml) and exhibited narrow antimicrobial spectrum among tested microorganisms. The compound was active against Pseudomonas aeruginosa ATCC 9027 (MIC 125 μg/ml) which is prone to causing infections that are difficult to treat due to it developing extremely rapid antibiotic resistance. In the antiproliferative studies, cell proliferation of the colon (HT-29) carcinoma cell line was significantly decreased after exposure to the compound. The results indicate that isoetin 4′-O-β-D-glucopyranoside possesses antioxidant capacity and very promising antibacterial activity and could have uses as an effective antipseudomonal agent as well a antiproliferative agent.

Hieracium pilosella herba (Fam. Asteraceae) is a component part of the French and the British Herbal
Pharmacopoeia. The following monographs exists:
- Piloselle published in the French Pharmacopoeia (Fr.Ph. 1996): Whole plant or fragmented plant of Hieracium pilosella L. Content: minimum 2.5 per cent of ortho-dihydroxycinnamic derivatives, expressed as chlorogenic acid (C16H18O9; MT 354.3) (dried drug)
- Pilosella (BHP): Pilosella consists of the dried plant of Pilosella officinarum C.H. & F.W. Schultz (Fam. Compositae), a stoloniferous, scapigerous herb up to 30cm in height, indigenous to the British Isles, Europe and Western Asia. Pilosella consists largely of leaf and contains the coumarin umbelliferone present predominantly as the 7-glucoside, the flavone luteolin and its 7-glucoside and other flavonoids, caffeic acid and chlorogenic acid.
The plant is small, 10-30cm long. Widely polymorphic, where the stump emits creeping stolons. The flowering stem is lonely, erect, hairy and it ends in a white capitule where the involucre is covered by glandular dark hair. The leaves are lanceolate, about 3cm long, greyish above with scattered slender
hairs and whitish underneath due to the dense covering of branched hairs. Flowers solitary, pale yellow, composite, about 2-3cm diameter, outer flowers often reddish underneath. The fruit is cylindrical and has simple, brittle tuft of hair (Paris, 1971). Taste, bitter, slightly aromatic; odour, faint (Wren, 1998).
Synonyms: Mouse-ear; mouse-ear Hawkweed

Constituents: (Bézanger-Beauquesne et al., 1980 ; Bruneton, 1998; Fournier, 1948; Garnier et al., 1961 ; Gruenwald, 2007; Paris and Moyse, 1971 ; Stanojevic et al., 2009; Van Hellemont, 1986; Wren, 1998)
Hydroxycoumarins: umbelliferone (mainly as 7-glucoside; about 0.60% of the dry plant material), skimmine
Flavonoids: luteolin, luteolin-7-glucoside, apigenin-7-O-glucoside (about 0.25% of the dry plant material), isoetin 4’-O-β-D-glucopyranoside (Gawrońska-Grzywacz et al., 2011)
Triterpenoids: alpha- and beta-amyrin, taraxerol, taraxasterol and fern-7-en-3-beta-ol (GawronskaGrzywacz and Krzaczek, 2007)
Organic acids: caffeic acid, chlorogenic acid (about 20% of the dry plant material)
Ascorbic acid
According to Stanojevic et al., 2009, the content of total phenolic compounds is about 240 mg gallic acid equivalents/g of dry extract, while total flavonoids content is close to 80 mg equivalents rutin/g of dry extract.