Da Ding Huang

A validated UHPLC-MS/MS method measured eriodictyol, dihydrokaempferol, dihydromorin, kaempferol, naringenin and morin in rat plasma and tissue, comparing normal rats with rats with acute liver injury, and an HPLC fingerprint of the crude drug was established alongside. Dihydrokaempferol-7-O-beta-D-glucoside and kaempferol were selected as quality markers on the strength of high in vivo exposure and good fingerprint resolution. This is the study that works on the correct article for the Chinese drug: the dried root, Radix Cudramiae.

Seventy per cent ethanol Soxhlet extract of the heartwood outperformed maceration and decoction on antioxidant capacity and total phenolic and flavonoid content, with morin as the major constituent by HPLC. At 500 mg/kg it markedly lowered uric acid in potassium oxonate-induced hyperuricaemic mice and inhibited hepatic xanthine oxidase ex vivo by about 53 per cent, and it suppressed lipopolysaccharide-induced proinflammatory transcripts in RAW 264.7 macrophages. The material is Thai heartwood, not Chinese root.

Aqueous heartwood extract inhibited alpha-glucosidase with an IC50 of 1.53 micrograms per millilitre. At 1000 mg/kg it lowered fasting blood glucose both in an oral glucose tolerance test and over 28 days of daily dosing in streptozotocin and nicotinamide-induced type 2 diabetic mice, with raised insulin levels. The authors describe this as the first study of the hypoglycaemic activity of the heartwood.

Ethyl acetate and methanol extracts inhibited herpes simplex virus type 2 with EC50 values of 38.5 and 50.8 micrograms per millilitre; the petroleum ether extract was inactive and the chloroform extract too cytotoxic to test. Bioassay-guided separation identified morin, which gave an EC50 of 53.5 micrograms per millilitre, while synthetic morin pentaacetate was inactive, indicating that free hydroxyl groups are required.

Hexane, chloroform, ethyl acetate, butanol and water fractions of an ethanol extract of the root wood all inhibited carrageenan-induced oedema in rats, the butanol fraction most strongly. Every fraction reduced serum transaminases and improved liver histology in carbon tetrachloride and D-galactosamine hepatotoxicity, with butanol and ethyl acetate best against carbon tetrachloride and chloroform best against D-galactosamine, the last comparable to silymarin. The material is the variety gerontogea, not the type variety.

Five flavonoids and five xanthones from the heartwood all reduced prostaglandin E2 synthesis in lipopolysaccharide-activated murine macrophages. 1,3,7-Trihydroxyxanthone and 1,3,5-trihydroxyxanthone were the most active, suppressing nitric oxide, prostaglandin E2 and proinflammatory cytokines by downregulating inducible nitric oxide synthase, cyclooxygenase-2 and PI3K/Akt while upregulating the M2 markers phosphorylated STAT6 and PPAR gamma.

Ten isoprenoid-substituted xanthones and a prenylated benzophenone from the roots were tested against vancomycin-resistant enterococci. Gerontoxanthone H inhibited five VanA, VanB and VanC strains at a minimum inhibitory concentration of 1.56 micrograms per millilitre; 1,3,7-trihydroxy-2-prenylxanthone, gerontoxanthone I, alvaxanthone and isoalvaxanthone were weaker at 3.13 to 6.25 micrograms per millilitre. In vitro only, with no data on whether these concentrations are attainable in a patient.

A validated HPTLC densitometric method quantified morin in heartwood from eight Thai provinces at 1.53 to 2.73 per cent. This is the only firm content figure available for any constituent of this drug and it applies to Thai heartwood; no equivalent figure exists for Chinese root material.

Heartwood from twelve Thai sources was fractionated and tested with its dominant compounds morin, resveratrol and quercetin against leukaemic K562, EoL-1 and KG-1a cells and in antioxidant and anti-inflammatory assays, with Wilms tumour 1 protein as the antileukaemic readout. Resveratrol was cytotoxic in all lines while extract fractions were selective, and the three major compounds had significant activity. Cell culture only, and the source-to-source variability is itself part of the finding.