Chlorophyll is the green pigment responsible for capturing light energy in plants, algae, and cyanobacteria. This molecule operates the process of photosynthesis, converting solar energy into chemical energy. Without this process, the global ecosystem would lack the primary energy source and the oxygen necessary for most organisms to survive. Due to its ubiquity in photosynthetic organisms, chlorophyll is the most abundant pigment in the world.
The Molecular Architecture of Chlorophyll
The chlorophyll molecule consists of a large ring-shaped head, known as a porphyrin ring, and a long hydrocarbon tail. The porphyrin ring coordinates a single magnesium ion at its center, which facilitates the initial absorption of light energy.
The porphyrin ring is hydrophilic, meaning it interacts well with water, while the phytol tail is lipophilic, or fat-soluble. This dual nature is essential for its function: the tail anchors the molecule securely into the lipid membranes of the plant’s cellular structures, while the head interacts with light and water.
The two most common forms, Chlorophyll A and Chlorophyll B, differ by only a single side-chain on the ring structure. This minor chemical variation allows the two types to capture light at slightly different wavelengths. Chlorophyll A primarily absorbs light in the violet-blue and orange-red regions, while Chlorophyll B absorbs slightly more in the blue and orange-red regions. This complementary absorption profile allows plants to maximize light capture across the visible spectrum.
Capturing Light: The Process of Photosynthesis
Chlorophyll molecules are precisely organized with proteins into large complexes called photosystems, which are embedded within the thylakoid membranes inside the plant’s chloroplasts. This structured arrangement ensures that captured light energy is efficiently transferred to the reaction center. Chlorophyll A acts as the reaction center pigment, directly initiating the conversion of light into chemical energy, while Chlorophyll B serves as an accessory pigment, funneling energy toward the reaction center.
The light-dependent reactions begin when light energy strikes the chlorophyll, causing an electron to become energized. This high-energy electron is then passed down a series of protein complexes known as the electron transport chain. To replace the lost electron, the photosystem complex splits a water molecule, releasing oxygen as a byproduct.
The energy released as the electron moves down the chain is used to pump protons across the thylakoid membrane, creating a concentrated gradient. This gradient is the driving force that powers the synthesis of adenosine triphosphate (ATP). The electrons are ultimately transferred to a carrier molecule, creating NADPH. Both ATP and NADPH are then used in the second stage of photosynthesis, the Calvin cycle, which takes place in the stroma and uses carbon dioxide to assemble sugar molecules.
Dietary Sources and Absorption
Humans consume chlorophyll by eating green vegetables. Common dietary sources include:
Spinach
Kale
Collard greens
Parsley
Wheatgrass
Broccoli
The native chlorophyll molecule is fat-soluble due to its long phytol tail, which affects how it is processed by the body. During digestion, the molecule undergoes transformation, often losing its central magnesium atom and phytol tail to form various derivatives, such as pheophytins and pheophorbides. While the overall absorption of the intact, native form of chlorophyll is low, recent studies have detected these chlorophyll-related compounds in the bloodstream after consumption of concentrated sources, indicating that absorption does occur.
Understanding Chlorophyll Supplements and Health Claims
Supplements typically do not contain natural, fat-soluble chlorophyll. Instead, they contain chlorophyllin, a semi-synthetic, water-soluble derivative. Chlorophyllin is produced by removing the lipophilic phytol tail and replacing the natural magnesium atom with a copper ion. This structural modification makes the compound easily dispersible in water, which is why it is often sold in a liquid form.
Chlorophyllin has a long history of use as an internal deodorant, particularly to reduce body odors associated with medical conditions like colostomies and fecal incontinence. This function is thought to be due to chlorophyllin’s ability to bind to odor-causing compounds in the gut.
In contemporary research, chlorophyllin has shown promise in preliminary studies related to skin health. Applying a topical gel containing chlorophyllin has been observed to help reduce facial acne and the appearance of large pores. It has also demonstrated potential in reducing signs of photoaging, or sun-related damage to the skin.
Furthermore, chlorophyll derivatives have antioxidant properties and the ability to form molecular complexes with certain cancer-causing agents, such as aflatoxins found in moldy grains. This binding mechanism can potentially block the absorption of these harmful compounds. A clinical trial showed that supplementing with sodium copper chlorophyllin substantially decreased a biomarker for aflatoxin-induced DNA damage. Despite these findings, many popular claims regarding supplements, such as boosting energy or promoting weight loss, lack sufficient scientific backing from large-scale human studies.