Herbal and natural medicines

what are herbal medicinal products (HMPs)

contains only herbs/plant material as active ingredients

• complex mixtures derived from plant material

• their active constituents are widely unknown

• have interactions between the chemical compounds in herbal medicines

what are the interactions between chemical compounds in herbal medicines

• may enhance activity and reduce likelihood of adverse effects

• interactions are additive/synergistic (as all compounds interact with each other to produce a greater effect than singular)

• different to natural products as, although they are plant derived, they are single chemical compound, herbal medicines contain a number of different chemical compounds

how do patients and the public see herbal medicines as

complementary or alternative

•  complementary → take a herbal product alongside prescribed medicine

• alternative → taken as a complete alternative to prescribed medication

what types of drugs can we derive from plants

• herbal drugs → derived from specific parts of a a medicinal plant (HMPs, herbal remedies, phytomedicines)

• natural products/compounds → isolated from nature (pure chemical entities used in the form of licensed medicines, now produced synthetically and referred as nature identical)

• nutraceuticals (functional foods) → foods with additional health benefits but only in the context of prophylactic activity, have preventive effects

give examples of herbal drugs we can derive from plants

• senna pods for laxatives and senna leaves for cognitive deficiency e.g. alhzheimer’s

• st john’s wort for low mood 

• german chamomile flowerheads for mild GI complaints and inflammation 

give examples natural products/compounds we can derive from plants

• morphine

• digoxin

• paclitaxel

• quinine

• caffeine

give examples of nutraceuiticals (functional foods) we can derive from plants 

• garlic → anti platelet to thin blood and reduce blood clots

• ginger → for nausea and vomiting

• turmeric →  anti-inflammatory agent

• carrots → vitamin A for function of retina

• cocoa → antioxidants for harmful free radical in body

• red wine → full of antioxidants for free radicals in body 

what specific plant organs of a plant species are HMPs derived from 

• aerial parts/herb (herba) → whole plant used

• leaf (folia)

• flower (flos)

• fruit (fructus)

• bark (cortex) 

• root (radix)

• rhizome (rhizoma) → underground stem, not root e.g. ginger

• bulb (bulbus)

• seed (semen) 

what do you need to know about a plant if you make a plant derived drug

• the species from which its obtained

• the name of plant

• the plant part used to produce the dried product

what does it mean if a product is considered to be adultered

if product contains the wrong parts e.g. if the product is supposed to contain leaf material, but has aerial material as well

what are the use of herbal medicinal products (HMPs)

• high level of expenditure: UK market rising

• mostly purchased OTC: general well-being/prevention and treatment of common ailments

• serious chronic illnesses; cancer, HIV/AIDS, MS, asthma

• elderly, pregnant/lactating women, parents administer to children 

what are the three routes that herbal medicinal products are regulated

1. unlicensed herbal remedies 

2. registered traditional herbal medicines

3. licensed herbal medicines

what are unlicensed herbal medicines

• don’t have to meet standards of safety and quality

• not required to have necessary information for a patient to use them e.g. safety warnings, contraindications etc

• normally sold on internet

what are registered traditional herbal medicines

the Traditional Herbal Medicines Registration Scheme (THMRS)

• need to meet specific standards of safety and quality

• accompanied by agreed indications and systematic patient information → allows safe use of the produce

• have a registration number to allow healthcare professionals and consumers to differentiate between a registered and unlicensed product,

  • registration is based on traditional use only, provided that the product has been medicinally used for a minimum of 30 years,

  • registration is not granted based on efficacy → no clinical trial data is provided

what are licensed herbal medicines

• demonstrate safety, quality and efficacy

• identified easily by distinctive product license number

• have proven efficacy in terms of clinical trial data

what is the difference between licensed HMPs and unlicensed HMPs

• licensed → GMP standard of manufacture

• unlicensed → no guarantee of pharmaceutical quality, safety and efficacy 

how do you assess quality and licensing of HMPs

look for:

• scientific botanical name (Latin binomial) of plant species 

• plant parts used

• type of extract and equivalent quantity of raw materials e.g. alcohol based/aqueous based

• standardised constituents and concentrations → if the chemical constituent is known, how much constituent is in the product

examples of latin binomials 

• Papaver somniferum → from opium poppy, induces sleep/drowsiness

• Digitalis Lanata (D.purpurea) → from foxglove, where we get digoxin from

• Taxus brevifolia → where we get paclitaxel from for anti-cancer treatment 

• Coffea arabica or C. robusta

• Matricaria recutita (L)

what are the issues with assessing quality

contamination

• Could be human error (misidentification of a plant species), or operators contaminating products on purpose

• Could be accidental or intentional contamination of PoMs e.g. corticosteroids for eczema

• Contamination of poisonous substances or heavy metals or pesticide residues

variable composition

• Natural → herbs don’t have a consistent standardised composition

• different parts of plant will provide different profile of chemical constituents

• concentration is influenced by factors such as climate, growing conditions, how its processed and dried

standardisation 

• standardised herbal products produced by several manufacturers to achieve a more consistent pharmaceutical quality

• Processed to contain a specific quantity of the active constituent, unwanted or toxic constituents can be removed but only if the active chemical constituents are known

• If we don’t know what the active constituents are, we can standardise using marker compounds. e.g. chemical characteristics of the plant that you know are present in larger quantities

what are other safety aspects we need ot consider with HMPs

these are all not well documented for herbal products 

• we don’t always know how active constituents are metabolised in the body and what metabolites we end up with