Sheng Di Huang

Sensory evaluation with twelve assessors, electronic tongue analysis, HPLC sugar and marker profiling across 17 batches, and molecular docking against human taste receptors were combined to track what steaming does to this root. Steaming significantly increased sweetness and reduced bitterness. Chemically, oligosaccharides hydrolysed to monosaccharides, with fructose up 15.99% and glucose up 8.90%, and the bitter iridoid glycosides degraded substantially, with catalpol falling by 88%. 5-Hydroxymethylfurfural was identified as a processing marker. This is the clearest quantitative account of what separates the raw drug described here from the prepared drug Shu Di Huang.

Rehmannioside A was tested against the major cytochrome P450 enzymes in human liver microsomes with marker substrate reactions. It inhibited CYP3A4, CYP2C9 and CYP2D6 with IC50 values of 10.08, 12.62 and 16.43 micromolar. CYP3A4 inhibition fitted a non-competitive model with a Ki of 5.08 micromolar and was also time-dependent (KI 8.47 per micromolar, Kinact 0.048 per minute); CYP2C9 and CYP2D6 fitted competitive models with Ki values of 6.25 and 8.14 micromolar. The authors concluded the compound or its source herbs may interact with drugs cleared by these enzymes.

Ethanol and water-ethanol extracts of Oldenlandia diffusa, Codonopsis tangshen, Rehmannia glutinosa and Astragalus propinquus were assessed for CYP3A4 inhibition in human supersomes and for induction in a PXR-mediated CYP3A4 reporter assay and by real-time PCR in LS180 cells. All four inhibited CYP3A4 with IC50 values between 17 and 83 microgram per millilitre, and Rehmannia glutinosa, along with Oldenlandia diffusa, significantly induced PXR-mediated CYP3A4. The authors concluded that induction could reduce the efficacy of narrow-therapeutic-index CYP3A4 substrates and called for clinical study. The extracts were made from raw material; the paper does not distinguish raw from prepared root.

Thrombosis was induced in rats with intraperitoneal type I carrageenan and Rehmanniae Radix extract was given at several doses. At 5.4 g/kg it significantly reduced thrombosis. Serum metabolomics found thirteen significant metabolites, most of which moved back toward control after treatment, and integration with network pharmacology pointed to PLA2G2A, PTGS1, ALOX5 and CYP2C9 as key targets, with catalpol, ferulic acid methyl ester and methyl 4-hydroxycinnamate as candidate actives. The targets are computational predictions supported by docking, not measured enzyme inhibition.

Rats were made diabetic with three weeks of high-fat, high-sugar feed followed by streptozotocin, then given catalpol by bolus intravenous injection at 0 to 50 mg/kg. At 50 mg/kg catalpol reduced weight loss, attenuated the rise in total cholesterol and triglycerides, raised HDL cholesterol, blunted the plasma glucose rise on oral glucose challenge, raised SOD, glutathione peroxidase and catalase, lowered malondialdehyde and reduced histological damage to the pancreas. The intravenous route is the limiting caveat: this does not establish that an oral decoction of the root delivers a comparable effect.

Four hundred outpatients with primary chronic glomerulonephritis were randomised to general acteoside of Rehmanniae leaves, two 200 mg tablets twice daily, or piperazine ferulate. After eight weeks the mean reduction in 24-hour proteinuria was 34.81% and 37.66% respectively, with the 95% confidence interval for the difference spanning zero, and no significant difference in erythrocyturia. Neither group changed eGFR or electrolytes and adverse events were low in both (1.5% versus 2.5%). Recorded here as an important caveat rather than as evidence for this drug: the preparation is made from Rehmannia LEAVES, not from Radix Rehmanniae, and the comparator is an active drug rather than placebo.

Twenty-two women aged 18 to 35 with moderate to severe acne were randomised to 100 mg per day of a Rehmannia glutinosa leaf extract or placebo for 56 days. Global Acne Grading System scores fell 21.72% with the extract and 14.20% with placebo by day 28, and the extract group reported better skin characteristics at day 56 with no tolerability concerns. This is a small proof-of-concept study, and again it uses the LEAF: it says nothing about Radix Rehmanniae, and is listed here only because it is routinely cited under the species name.