Rosmarinic Acid: The Plant Compound from Rosemary, Lemon Balm and Sage

Anyone who uses rosemary, lemon balm, or sage in the kitchen has almost certainly consumed rosmarinic acid without realising it. This plant compound is named after rosemary, but it occurs in a whole range of culinary herbs. In this guide, we explain what rosmarinic acid is chemically, which plants it's found in, and what to look for when choosing herbs and extracts.

What Is Rosmarinic Acid?

Rosmarinic acid is a secondary plant compound from the large group of polyphenols. Chemically, it is an ester of caffeic acid and another phenolic compound (dihydroxyphenyllactic acid). This makes it one of the so-called hydroxycinnamic acid derivatives, a widespread class of plant pigments and aroma compounds.

Secondary plant compounds are substances that plants don't produce for their basic metabolism, but rather, for example, to defend against predators, cope with environmental stress, or serve as pigments. Rosmarinic acid is one of the better-known representatives of this group of compounds and is a subject of food and plant research. It gets its name because it was first isolated from rosemary.

Within the polyphenols, rosmarinic acid can be classified among the phenolic acids, more specifically the esters of hydroxycinnamic acids. This group of compounds also includes the widespread chlorogenic acid found in coffee and ferulic acid found in grains. What sets rosmarinic acid apart is its good water solubility, which is why a considerable proportion transfers into the water when brewing herbal tea. Within the plant itself, it is found mainly in the leaves and contributes to the typical herbaceous, aromatic taste of many mint-family plants.

Where Does the Name Come From, and What Synonyms Exist?

The name derives from the Latin Rosmarinus officinalis, the plant from which the compound was first obtained – hence its English name, rosmarinic acid. Older sources occasionally use the term "labiatic acid", named after the mint family (formerly Labiatae, now Lamiaceae), in which it occurs particularly often. Rosmarinic acid shouldn't be confused with rosemary oil (the essential oil) or with carnosic acid, another rosemary compound. You can find out more about the plant itself in our guide to rosemary and its uses.

Which Plants Contain Rosmarinic Acid?

Rosmarinic acid is typical of the mint family (Lamiaceae), which includes many classic culinary and tea herbs. It is found in particularly high amounts in:

• Rosemary (Rosmarinus officinalis) – the plant it's named after
• Lemon balm (Melissa officinalis) – considered one of the richest sources
• Sage (Salvia officinalis)
• Peppermint and other mints (Mentha)
• Thyme, oregano, basil, and marjoram

The compound also occurs outside the mint family, for example in certain borage and plantain family plants. However, the exact content varies considerably depending on plant species, variety, harvest time, growing location, and processing. Fresh, aromatic herbs and gently dried goods generally contain more secondary plant compounds than herbs that have been stored for a long time. If you're interested in choosing sage, you'll find tips in our article Buying Sage: What to Look For.

Why Does the Plant Produce This Compound?

For the plant, rosmarinic acid is no accident. As a secondary plant compound, it performs protective functions in the leaf tissue: it belongs to the chemical defence arsenal that mint-family plants use to guard against microbial attack, predators, and environmental stress such as intense sunlight. Such compounds are often produced in greater amounts when a plant is exposed to adverse conditions. This also explains why herbs from sun-drenched, sparse locations – such as Mediterranean outdoor-grown herbs – are often especially aromatic: aroma and the content of secondary plant compounds are closely linked. For us, this mainly translates into a more intense flavour in the kitchen.

In What Forms Do We Encounter Rosmarinic Acid?

The most obvious way to take it in is through diet: via fresh or dried culinary herbs, herbal teas made from lemon balm, sage, or peppermint, and Mediterranean dishes that make generous use of rosemary and oregano. Rosmarinic acid is therefore a natural part of a herb-rich, plant-focused diet. Especially in Mediterranean cooking, where herbs are used generously, a notable amount adds up over the course of a day – without you needing to count individual compounds.

Extracts and Concentrates

Standardised extracts are also produced from lemon balm, rosemary, or sage for use as an ingredient in food supplements or foods. Rosemary extract is additionally approved in the EU as a food additive (E 392) and is used technologically as an antioxidant to protect fats and oils from turning rancid. In this role, it's about the shelf life of the food, not an effect within the body.

Food Supplements

In food supplements, rosmarinic acid is usually not found in isolated form, but as part of a plant extract, for example from lemon balm leaves or rosemary leaves. Such products are legally classed as foods and are intended to supplement a normal diet, not replace a varied one.

Preparation: How to Retain as Much as Possible

Because rosmarinic acid is highly water-soluble, preparation plays a role in how much of it ends up in the finished dish or drink. A few practical pointers:

• Herbal tea: Freshly brewed lemon balm, sage, or peppermint teas release water-soluble plant compounds into the infusion. Letting it steep, covered, for a few minutes helps release more aroma and active compounds.
• Fresh herbs: Added towards the end of cooking, aroma and heat-sensitive components are better preserved than with prolonged cooking.
• Storage: Dried herbs are best kept in a dark, dry, airtight container. Light, oxygen, and moisture gradually break down aroma and plant compounds over time.

These tips relate solely to flavour and the preservation of natural compounds – they are not a promise of any specific effect in the body.

Rosmarinic Acid in the Diet: Putting It in Context

Rosmarinic acid is one of many thousands of secondary plant compounds we take in through plant-based foods. Nutrition professional bodies generally recommend a varied, plant-focused diet rich in vegetables, fruit, herbs, and spices – not the targeted intake of individual isolated compounds. Anyone who eats plenty of fresh herbs, salads, and Mediterranean dishes automatically takes in polyphenols like rosmarinic acid, in their natural combination.

There is no authorised EU health claim for rosmarinic acid itself. Statements about specific health effects are therefore not legally permitted and would also not be scientifically defensible. Here, we deliberately describe the compound only as a natural plant constituent and part of the diet. If you'd like to explore polyphenol-rich foods more broadly, you'll find an overview in our guide to antioxidant-rich foods.

What matters is seeing this in the overall context: no single plant compound makes a diet good or bad. The benefit of a plant-focused diet comes from the interplay of countless components – fibre, vitamins, minerals, and the whole range of secondary plant compounds. Rosmarinic acid is an interesting piece of this mosaic, but no more than that. Anyone who deliberately reaches for fresh herbs, salads, and Mediterranean dishes doesn't need to worry about the intake of individual compounds.

How Can You Recognise Good Quality?

Whether as herbs, tea, or extract – for products meant to offer a meaningful content of rosmarinic acid, it's worth looking at a few points:

• Origin and freshness: Aromatic, strongly scented herbs suggest a good level of aroma and plant compounds. Gentle drying and storage protected from light preserve the compounds better.
• Clear labelling: For extracts, it should be clear which plant and which plant part (leaf, herb) the extract comes from, and whether it is standardised.
• Purity and testing: Reputable suppliers have their raw materials tested for heavy metals, pesticides, and microbial contamination. If in doubt, ask for certificates of analysis.
• Realistic claims: Be cautious of products making specific promises of a cure – this isn't permitted for foods and food supplements and is a warning sign of an unreliable supplier.

For everyday life, the takeaway is this: if you already enjoy cooking with herbs and drinking herbal teas, you're covering your intake of such plant compounds in a pleasant and inexpensive way. Extracts and food supplements are one option, but not a requirement. If you have an existing health condition, are pregnant or breastfeeding, or take medication, you should check with a doctor before using concentrated plant extracts, as different standards apply here than for a pinch of herbs in your food.

Frequently Asked Questions (FAQ)

Is rosmarinic acid the same as rosemary oil?

No. Rosmarinic acid is a single, water-soluble plant compound from the polyphenol group. Rosemary oil, on the other hand, is the essential oil of rosemary, a mixture of volatile, fat-soluble aroma compounds such as cineole and camphor. Both come from the same plant but are chemically completely different.

Which herbs contain the most rosmarinic acid?

Mint-family herbs such as lemon balm, rosemary, sage, peppermint, thyme, and oregano are particularly rich. Lemon balm is considered one of the most abundant sources. The actual content can vary considerably depending on variety, cultivation, harvest time, and processing.

Can I get rosmarinic acid through a normal diet?

Yes. Anyone who regularly uses fresh or dried culinary herbs, drinks herbal teas, or cooks Mediterranean-style takes in rosmarinic acid quite naturally through food – embedded in the natural variety of other plant compounds.

What does the ingredient E 392 mean on food labels?

E 392 stands for rosemary extract, which is approved in the EU as a food additive. It is used technologically to protect fats and oils in food from turning rancid and to improve shelf life. This relates to the product, not to any effect within the body.

Are food supplements with rosmarinic acid necessary?

Food supplements are legally intended to supplement a normal diet, not replace a varied, plant-focused one. Whether such a product makes sense for you is best discussed individually with a doctor or a nutrition professional.