Exhibit 10.4

*** Indicates omitted material that is the subject of a confidential treatment
request filed separately

with the Commission.

AMENDMENT TO PURCHASE AGREEMENT

THIS AMENDMENT TO PURCHASE AGREEMENT (this “Amendment”) is effective as of the
_6_ day of _May_ 2008_, by and between MARINOVA PTY. LIMITED (hereinafter
“Seller”), with its principal place of business located at 249 Kennedy Drive,
Cambridge TAS 7170, Australia, and MANNATECH (INTERNATIONAL) LIMITED
(hereinafter “Buyer”), a Gibraltar corporation, with its principal place of
business located at 10/8 International Commercial Centre, Casemates Square,
Gibraltar.

 

  A. Buyer and Seller are the current parties to a PURCHASE AGREEMENT dated
April 27, 2007 (the “Agreement”), under which Seller agreed to supply to Buyer,
agreed amounts of Undaria pinnatifida fucoidan (“GFS 75% powder” or “Product”)
from Seller for use in its proprietary nutritional supplements and topical
products and Seller desired to supply the Product to Buyer.

 

  B. The parties desire to amend and revise the Agreement for the purpose of
extending the term and increasing the amount of Product for purchase. Any
capitalized terms used in the Amendment shall, unless otherwise specified
herein, have the same meaning ascribed to such terms as set forth in the
Agreement.

NOW, THEREFORE, the undersigned parties, in consideration of the mutual
covenants contained herein and for the good and valuable consideration the
sufficiency of which is hereby acknowledged, agree as follows:

 

1. Amendment to Purchase Agreement. Notwithstanding anything to the contrary
which may be contained in the Purchase Agreement, the Purchase Agreement is
amended so as to reflect the following:

(a) Extension of Term

The first sentence of Paragraph 1.1 of the Agreement is amended to read,

“The term of this Agreement will commence on 15 August 2007 and, unless sooner
terminated in accordance with this Agreement, continue through 14 August 2012
(the “Term”).”

(b) Exclusivity

Paragraph 6.1 is amended to read,

“Buyer shall have a worldwide exclusive right for Tasmanian harvested Undaria,
as well as GFS extracted from Tasmanian harvested Undaria, throughout the Term
of this Agreement (or any renewal thereof) in the nutritional sector provided
that Buyer satisfies its obligation to purchase the minimum volume commitments
set forth in Exhibit B and otherwise complies with its obligations under this
Agreement. Seller shall not directly or indirectly develop,

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manufacture or market an “equivalent or derivative product” for any other
multi-level marketing, direct sales or similar company, or any other form of
retail distributor or intermediary using the Tasmanian harvested Undaria during
the Term of this Agreement or any renewal thereof. For the purpose of this
Agreement, “equivalent or derivative product” means any product formulated by
Seller that substantially replicates the Product or other GFS product ranges as
to the combination of specific ingredients, nutrients, and functional features.”

(c) Exhibit B: Product Amount and Price

Exhibit B of the Agreement is amended so that the following is added to the
Exhibit,

“Between 15 August 2009 and 14 August 2010 (“Year 3) Buyer shall purchase a
minimum of *** Kilograms of Product at a rate of *** per kilogram. Seller shall
be responsible for the payment of freight to the Buyer’s Dallas, Texas
distribution center.

Between 15 August 2010 and 14 August 2011 (“Year 4”) Buyer shall purchase a
minimum of *** Kilograms of Product at a rate of *** per kilogram. Seller shall
be responsible for the payment of freight to the Buyer’s Dallas, Texas
distribution center.

Between 15 August 2011 and 14 August 2012 (“Year 5”) Buyer shall purchase a
minimum of *** Kilograms of Product at a rate of *** per kilogram. Seller shall
be responsible for the payment of freight to the Buyer’s Dallas, Texas
distribution center.

 

2. Integration; Modification. This Amendment contains the entire understanding
between Seller on the one hand, and Buyer on the other hand, with respect to the
subject matter of this Amendment and this Amendment supersedes all prior or
contemporaneous oral or written agreements, conditions, or representations. This
Amendment may not be amended, canceled, or superseded, nor will any provision of
this Amendment be deemed waived, except by a written instrument executed by each
of the parties to be charged.

 

3. Binding Effect. This Amendment will be binding upon, and inure to the benefit
of, the parties and their respective heirs, legatees, personal representatives,
successors and assigns.

 

4. Counterparts. This Amendment may be executed in one or more counterparts,
each of which will be deemed an original, but all of which, when taken together,
will constitute one and the same instrument.

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IN WITNESS WHEREOF, the parties have executed this instrument as of the date
first above written.

 

MARINOVA PTY. LIMITED By:  

/s/Nick Falk

Name:   Nick Falk Title:   Business Development Manager MANNATECH
(INTERNATIONAL) LIMITED By:  

/s/ Stephen D Fenstermacher

Name:   Stephen D Fenstermacher Title:   CFO